Harley Goes Wobbly on Twin Cam

Since Harley came out with their Twin Cam in 1999, it has gained a reputation as a motor that is fairly easy to modify for significant horsepower gains. Unfortunately, the Twin Cam's reputation for reliability seems to have lagged far behind, and not without reason.

First there was the whole fiasco with the early cam chain tensioners. Seemed as though the life expectancy was anywhere between 20 and 30 thousand miles (though some did not make it that far). When they wore through the tensioner pad, things could get ugly in a hurry. Throw a little hearing loss on the owners part, and you get a cam chain wearing a hole through the cam cover (its true - I just rebuilt one with just that problem).

An early response to the whole cam chain tensioner problem was the S&S gear drive cam set up. Its a legitimate fix, but it comes with its own issues, the main one being gear lash. Of course the whole idea behind the cam chain set up from Harley was to quiet the motors down by eliminating gear lash issues. Only trouble with the gear drives is you now have two sets of gears to get the lash right in order to have a quiet motor; the outer pair which drive the rear cam off the crank, and the inner pair which drive the front cam off the rear one. Although S&S offers and oversize and and under size gear for each pair to aid in getting a good fit, every cam plate will give a different fitment. Too tight on the lash and the gears will whine; too loose and you get the old tappet type noise.

After only seven years in production, the factory came up with a new solution for the early cam chain tensioner failure syndrome. Beginning with the 2006 Dyna models, and 2007 for the balance of Big Twins, Harley fit the Twin Cams with a new type cam chain system known as variously as hydraulic tensioned, or silent cam chains. Apparently the key to this new system is not so much the hydraulic tensioner as it is the type of chain itself. A quick feel of the outside edge of the chains (the part that the tensioner pads ride on) tells the real story. The early chains which were controlled by spring loader tensioner pads are down right sharp compared to the later chains!

All that leads us to that venerable practice of upgrading old motors with later model part. Really, it is a custom that has flourished for many years, and involves everything from putting on an M74 carb in place of your M35, all the way up to the simple but ambitious practice of putting an entire Shovel top end on a Pan. The "late model parts on an earlier model bike trick" has been a staple of the Harley aftermarket as well as the Motor Company itself for years.

The first I became aware of the possibility of upgrading the cam tensioners on '99-'06 Twin Cams was via the Kuryakyn catalog. They even list all the parts you need to purchase from your local Harley dealership to complete the upgrade. Included in the upgrade is the late model cam plate and the new higher volume oil pump, and of course Kuryakyn will be happy to supply a variety of cam grinds manufactured especially for this upgrade.

Checking the Andrews catalog, I see they offer a whole kit with cam plate, oil pump, and everything else needed for the conversion as well as a full complement of cams specifically for this upgrade.

Not to be totally outdone, Harley Davidson, via their Screamin' Eagle division also offer a kit. Harley's kit, however, leaves you stuck using the original "chainsaw" style inside cam chain. The reason they did this was so that you do not have to use a special cam; you can keep the one you have if it is still usable. The down side is that you are forced to keep the chain that contributed to the problems in the first place, and is the one hardest to service to boot. Seems to me it is only a solution to half the problem.

Now, if you are thinking that you lean toward the Kuryakyn promoted solution, I have a couple of cautions for you. Since you are purchasing a cam plate that is not designated for use on the '99-'06 engines there won't be any warning label mentioning that on certain years of NON Softail models, one of the oil holes in the new cam plate will line up with ...NOTHING. That right, if you have a '99 (for instance) Dyna or FLT model, this hole which feeds the balance chain tensioners on "B" motors, will dump pressure oil directly into the cam chest. This will drastically lower your oil pressure, give you noisy lifters, and a flickering oil pressure light at hot idle. The solution is to simply plug the hole; in fact the procedure would have been outlined for you in the instructions if you had purchased a stock replacement cam plate for your early Twin Cam.

this is the offending oil hole

where the boss would be on B motors - note the pencil is pointing at open space

the solution

The next caution has to do with cam sprocket alignment. From what I have seen so far, I am led to believe that Harley has machined every pinion shaft from 1999 until now incorrectly. Every shaft is machined for the diameter of the cam chain drive sprocket just inboard from the portion that rides in the cam plate itself. This machining includes a "flat" on one side which positively locates the sprocket. This machined flat is the problem. Admittedly I have only checked a half dozen crank assemblies, but the range from 1999 to two brand new fresh out of the shipping crate 103" cranks. The specific problem is that the "flat" is machined deeper (further inboard) that the rest of the diameter for the sprocket by about .015". This causes the cam chain sprocket to pull in on that side when tightened. It gives said sprocket a similar amount of lateral runout, which in turn makes sprocket alignment between cam and pinion, shall we say ...interesting.

undercut deeper at the flat

There's not much you can do about the situation, as far as I can see, outside of being aware of the issue so that you can split the difference and minimise the misalignment between the two sprockets. If you were to simply follow the factory service manual and check the sprocket alignment, adjusting to within the Harley mandated .010, you may not think to turn the motor over 180 degrees and re-check. You may not think to, because the manual doesn't mention it. Whoever wrote the manual assumed (as most of us do) that the sprockets would install "square" on the shaft. Oops.

note gap between straight edge and top sprocket

rotate engine 180 degrees and note difference in gap

Now you "get" the title that I chose for this piece; "wobbly" indeed. If that were the only place the factory went wobbly on the Twin Cam, it would be one thing, but it seems to be only the "tip of the iceberg", so to speak. How about the flywheels? Why is it that the specification for flywheel runout on my 1946 Knucklehead is within .001", but on a new Twin Cam it has become four times as much at .004"? Is that progress? Were the machine tools that much more accurate back then?


A comparison of a 1999 Twin Cam service manual with its 2009 counterpart is revealing. In 1999 the spec for flywheel runout was .002 maximum. By 2009 that spec was doubled to .004". Not only that, but the service wear limit (deemed acceptable by the factory before repair) in 1999 was .003 for flywheel runout, but .005" ten years later. Note that the .003" runout which was the limit before replacement in 1999 would be within new setup spec for 2009. In 1999 the spec for pinion shaft runout was .003, and no service wear limit was given. In 2009 that spec, though renamed (to protect the guilty?) is .010" with a whopping (or should I say wobbly) service wear limit of .012!

My conclusion? Harley reached its zenith for quality and engineering with the Evo motor. Of course they reached their zenith in just plain "class" much earlier with the Knucklehead!

Setting Pinion to Cam Gear Lash

This is one of those tech tips that I have considered writing several times, but each time I considered it, I decided to put it off until I could provide some pictures to go along with it. But, it seems that I never have an engine at that point when I think of doing this post, and never remember to take pictures when I do. So, we're all going to have to tough it out without pictures, as though we were adults.

Noisy motors are something that are a source of annoyance, and sometimes even embarrassment. The following is directly applicable to Big Twin from 1940 to 1999 as well as most S&S motors, and also can be applied to some extent to Flatheads and Sportsters. With the abundance of cams on the market, and the frequency with which they are changed, whether due to wear or for performance, this is always a timely subject.

First things first. Let's debunk an old wives tale having to do with "a matched gear set." While old wives are the best kind to have, particularly if you are an old husband, it has been my experience that they are an unreliable source for Harley technical advise. The "myth" of the matched gear set stems from the fact that the Factory did (maybe still does) sell a cam and pinion gear set. Trouble is, all that means is that the set comes with both gears in the middle of the size range. There are absolutely no guarantees that size combination will be correct for your engine. After all, if the factory could make a gear set that would fit all of their motors correctly, there would be no reason for them to make more than one size pinion gear and one size cam gear.

But they do, and they have since sometime back in the 1970's. The reason is to compensate for manufacturing tolerances in the center to center distance between the pinion shaft and the cam bearing in the crankcase as well as the pinion bushing and cam bushing in the cam cover. What did they do before different gear sizes were available you ask? Well, I guess you just had to live with a little extra noise.

Now, it is important to note that there are two separate types of bad fitment that will lead to noise: too tight and too loose. Too tight is actually a much bigger problem than its opposite. Too tight a fit between the pinion gear and the cam gear will result in a pronounced whine, and whining is never a good thing whether it emanates from your friends or your engine. In the latter case, it can lead to localized overheating and destruction of the gears. In the former cases it can lead to localized overheating of your temper. Neither is a good situation but the situation with your engine is easier to remedy.

Too much lash between the cam and pinion gear, on the other hand is generally harmless. Annoying but harmless. In fact, often times, a set of perfectly innocent lifters will be blamed for the "ticking" noise caused by pinion gear fitment. But lets get to the point of this post. Setting up proper cam to pinion gear fitment.

When installing a cam and pinion gear combination of unknown fitment, I have found that the best way is to test fit the combo, and be prepared to spend some time getting it right. If dealing with a rebuild where bushings have been replaced, it is worth installing the cam gear in the case without a pinion gear. This is particularly important on an early engine which uses a bushing in the crankcase rather than the late style Torrington. Install the cam with some lube on each end, and without a spacer or thrust washer. Once the cover (with gasket) is tightened, the cam should rotate freely with only light finger pressure. If the cam is binding in the two bushings you need to address that first so that you will be able to "feel" the fitment after you add the pinion gear.

Now that you know the cam is not binding, you can install the pinion gear, cam (again without thrust washer or spacer) and cover. Reaching in through the lifter block hole you should be able to slide the cam in and out easily. That is why you left the spacers out; so there would be plenty of end play to give a good feel. If you cannot slide the cam back and forth easily with just finger pressure, then it is too tight and it will whine.

So, what if by some stroke of luck the cam slides easily back and forth at this point? Are you done? Fat chance. This party is just getting started! If the cam does slide easily without bind, you need to check this at different points in its rotation. That means turning the engine over by hand. If the engine is in the chassis, jack the rear wheel up and with the plugs out and the trans in high gear, turn the wheel to rotate the engine. You will want to check the fitment at at least four places in the cam's rotation. If you find a place where the cam does not slide easily, it is too tight. If the cam will slide easily throughout its rotation, you have established that the fitment is not too tight.

The next step is to check to see if it too loose. Again, reach in through the lifter block hole but this time try to move the cam back and forth in its rotation. If you can feel, or hear a slight click as you move the cam back and forth, it is looser than you would like. Proceed as before and check this fitment in multiple locations in the cams rotation. Perfect fitment is when the cam can be easily slid in and out at any point in its rotation and likewise no lash can be felt or heard when attempting to move it back and forth.

Trouble is, you will rarely find a combination that is perfect. The culprit again is manufacturing tolerances. If the the cam gear and the pinion gear were each perfectly concentric and the crankshaft had zero runout, then there would be no need to check the fitment at more than one place in its rotation. But they aren't and so you do.

The next step, as you have likely already guessed, is to try another size pinion gear, but before you do, it might be helpful to make some notes of what you just found with the present combination. Personally, I always check the fitment every 90 degrees (4 places) in the cams rotation. My note might look like this: blue gear very loose 3 of 4/ slightly loose 1 of 4. The logical next step would be to try the next size larger pinion gear.

Conveniently both S&S and Jim's Machining offer a full range of color coded pinion gears. Though there are pins available which enable you to measure the gears, I find that they are really only of much use when dealing with a gear whose color code is no longer legible. Other than that, simply consult the color code chart from the appropriate catalog to guide you in selecting the next gear to try.

From there the process is repeated with your next selection of pinion gear. Use some common sense here. If the fitment was either extremely loose or tight, you might want to skip one color size to speed the process up. Remember, you will seldom get a "perfect" fitment between the gears, but you will always be able to get a "best possible" fitment - even if you wind up trying every pinion gear available. That is where those notes can come in very handy. Don't be surprised if you wind up going back to a size you already checked as the best possible combo.

One thing you want avoid is a situation where the the fitment is tight at any point in its rotation. Say for instance the fitment feels good 3 of 4 spots in the cams rotation, but is tight enough in one spot that you cannot slide it back and forth with just finger pressure; that combination will whine! I once had a cam that felt good in every place in its rotation with the exception of a short span of one or two teeth, where it took a screwdriver to pry the cam back and forth. I decided to try it, and surprisingly, it was a real whiner! The best coarse of action in such a (rare) case is to replace either the cam or cam gear. Hint: If a combination is tight in two spots in the cams rotation,180 degrees apart, the discrepancy is in the pinion gear or crank runout (since the pinion gear rotates twice for each rotation of the cam). Conversely, if there is only one tight spot, the out of round issue lies with the cam gear.

The best possible fit will be the largest pinion gear that has no bind. Don't be surprised if it checks something like this: good 1 of 4/slight lash 2 of 4/lash 1 of 4.

I guess by now it has become clear that it is beyond the reach of most guys installing their own cam to obtain the "best possible" cam to pinion gear fitment, what with 8 different sizes of pinion gear available, and each of them retailing for over $80. If you then multiply that by the four different styles of pinion gear (splined for Knuckles and early Pans, full length tapered for late Pans and early Shovels, stepped tapered for late Shovels and early Evos, and then of coarse late Evos) at least you can see why your local shop doesn't work for free.

So what are you to do? Well, the cam manufacturers know the danger of fitment that is too tight. That means that they provide cam gears that are on the small side of medium so you are much less likely to have a tight fitment than a loose one. A little ticking caused by gear lash won't hurt anyone, but the whining.... that's got to be fixed, unless of course it is coming from your friends, in which case there may be no cure.

Bulletin Board Worth a Look

A couple weeks back I received an email from a gentleman in Holland with a link to his bulletin board. Max and Frits are the ones who have communicated with me, and I have to say, they definitely think out-of-the-box compared to the Harley tech you are likely find here stateside. The vintage Harley motors seem to be of particular interest to them. All of you gearheads out there would do well to take a look.

A couple warnings though. The site is in the Dutch language. Now my Google toolbar has the capability to translate the pages for me, and it likely will not be too tough for you to figure out how to do the same. However, even with the translation tool, it is tedious reading (at least for me), not because of how it is written, but because of the limitations of the translating tool. If you take a look, you will see what I mean.

The second warning has to do with attitude. I never would have expected myself to react this way, but I find myself having to fight off the tendency to get defensive about America's pride and joy - the Harley. You know the way it goes; its one thing for me to bad mouth the technology on a Harley, just don't try it if your not from here. But a little introspection goes a long way, and it is quite obvious after a little thought that these guys are enthusiasts just like us, otherwise they would not take the time to devote a bulletin board to the subject.

There is also a second warning having to do with translation. I think some comments that may come across as insulting, may be the result of the translation tool. For instance, if someone states that you are ignorant, it will certainly get your hackles up. If on the other hand the same idea was translated "did not know," then no problem. Well, at least no problem unless you always think you are the smartest person in the room. I try not to make that assumption about myself, and it usually proves to be true. Just try to read it giving the guy on the other end of the Internet the benefit of the doubt on such things and it will be a lot more enjoyable. I could quote a Bible verse here, but I will spare those of you who are here for the motor stuff.

So, what about that link? Here it is: Motor Vitamine

Check it out, I think you will find it interesting.

Cheap Shop Tool

The material I have for posts is beginning to stack up. I have been too busy in the shop to post very often, despite very few interruptions as I worked through Sturgis week. I have several short items that I hope will get me back on track, and keep you the reader interested.


This may only be useful if you are "in the business" or do a lot of your own work, but if you have access to a lathe, it is a no-brainer.

The "Old School" method of squaring a piston ring in the cylinder bore for checking end gap usually involves putting the ring into the bore, and then using one of the pistons to push it down evenly. There are only two problems with that method (that I can see). First, since the top of the piston is smaller than the skirt, it is easy to have the piston cocked a little, which will throw of the end gap measurement. The other problem, is that if your piston has a dome, then there is also the chance that the dome will not square up the ring properly.


Of course, if you happen to have some junk flat top pistons laying around your shop gathering dust (and what motorcycle shop doesn't?) your project is nearly done. Simply select a piston from the next standard bore size larger than the one you need a squaring tool for, chuck it up in your lathe, and turn the top two ring lands down to just under standard bore size. De burr, wash, and you're done. By machining down the top two ring lands, when you push the ring into the bore with your new tool, the third ring land will stop on the head gasket surface leaving your ring about 1/2" into the bore, and perfectly squared up!

883 piston cut for use on 45" Flathead

For example, I used an 883 Evo piston cut to just under 2 3/4" for use on 45 Flathead motors. I made a 3 7/16" tool for Knuckles/Pans/Shovels from a stock 80" Evo piston, a 3 1/2" Evo tool from a 3 5/8" S&S piston, and a 3 5/8" tool from a stock 88" Twin Cam piston. In the near future, a 95" Twin Cam piston will provide the raw material for a 3 3/4" Twin Cam 88" tool, a 4" S&S piston for a 3 7/8" Twin cam, and a 4 1/8" S&S piston for a 4" .

The best part is that all it should cost you is a minimal investment of time!

Proof of Reverse Evolution

I just read in V-Twin News (not to be confused with the similarly named purveyor of questionable quality parts) that Harley Davidson is in process of introducing a new parts numbering system. The quite understandable problem is that they were running out of available digits in the old system.

Let's back up for just a moment. Harley's first (to the best of my knowledge) parts numbering system was quite simple. My 1926-1939 Harley parts catalog starts with part number 2-24 and ends with 7424-32. The two digits at the end indicated the year of introduction of the part. Simple yet effective, however as time went one, no doubt available digits became scarce.

The next parts numbering system is the one that we all know and love, and is the one that was in use well before I was turning wrenches for a living. This system uses, for most major parts, five digits and then a dash followed by the year of introduction of that part, just as the earlier system did. For example, in the earlier system, a tappet roller for 45" Twins was 208-29. In the later numbering system, the same part was 18535-29. From what I understand all of the current part numbers will remain valid, and only new parts coming on line will receive the latest part numbering system.

So, "what is your point and what in the world does it have to do with your title?" you are no doubt wondering. Well, just this; It seems that the more we know, the dumber we get. I once heard that the normal human brain can comfortably keep four numbers in it's short short term memory. I prove that to myself every time I have to write account numbers on checks as I pay bills. Try it for yourself. Look at your credit card. Broken down into four sets of four digits, it is simple to copy onto a piece of paper. Now put those 16 digits down on paper without any spaces or dashes. Copy them now. Not so easy is it? Better yet, now double check your work!

Now, I suppose no one employed by Harley Davidson had ever heard of such a thing (or at least none of those in charge of coming up with the new numbering system). But did anyone even consider asking a parts counter man what he thought? Here is a sample part number as given in the V-Twin News article: 34500008. That's right, eight digits with no spaces. And the introduction year? Well, that info will be available, but no longer contained in the part number itself. If you are still having trouble counting the zeros in that sample, here's a hint. Count the number of other digits, and subtract from eight.

I am sure there won't be any mis-ordered parts due to this system! (sarcasm) Obviously the person who came up with it never had to look in a parts book and then walk back to a shelf to find the part. and there's nothing like waiting for a special order part for a week, so that you can finish a job, only to find you copied one number wrong and bought a $900 crank assembly instead of the $1 gasket that you needed.

There is no doubt that the human race is gaining more knowledge all of the time. We are in the "Information Age" as it is called, but information is not the same thing as intelligence, and it certainly is not the same thing as common sense. The new Harley parts numbering system? Just a silly little inconsequential example of not looking before you leap, or else a prime example of how you can't teach an old dog new tricks ......whichever way you prefer to look at it.

Handy Cam Formulas

Last week I found myself doing a little research on cams for a certain application. As part of that project I ran into some specs that were not always published with each cam manufacturer. I decided to make a list of some cam formulas to help fill in some of the blanks. Some of these are self evident, and others not so much. These may have been published elsewhere, but I did not copy them. The last four listed here are of my own "invention" brought about by one particular cam grinder listing some of his cams with the duration @ .053 but not the specific opening and closing at that .053 event. If my equations look a little odd, it is because it was the best I could do to make them readable with "Blogger" formatting

INTAKE DURATION = 180 + INT OPENING + INT CLOSING

EXHAUST DURATION = 180 + EXH OPENING + EXHAUST CLOSING

INTAKE LOBE CENTER = (180 + INT CLOSING minus INT OPENING) divided by 2

EXHAUST LOBE CENTER = (180 + EXH OPENING minus EXH CLOSING) divided by 2

LOBE SEPARATION ANGLE = (INT LOBE CENTER + EXH LOBE CENTER) divided by 2

INTAKE OPENING = (INT DURATION divided by 2) minus LOBE CENTER

INTAKE CLOSING = DURATION minus 180 minus INTAKE OPENING

EXHAUST CLOSING = (EXH DURATION divided by 2) minus LOBE CENTER

EXHAUST OPENING = DURATION minus 180 minus EXHAUST CLOSING

You may notice a trend here, in that the constant "180" is used in many of these formulas. That is because most cam specs are given in degrees Before Top Dead Center / After Bottom Dead Center, etc. rather than using a full 360 degree scale. For example, an intake valve may be opened at 15 degrees before the piston reaches TDC on the "power" stroke. It will remain open for the full 180 degrees of the "intake" stroke, and then close at 31 degrees after BDC of that intake stroke. Add those three figures (15 + 180 + 31) and you get the 226 degrees of duration as listed for an Andrews EV13 cam.

note: if anyone has any corrections to any of these formulas, please let me know. I am working from a 40 year old high school education, and I often wish I had a couple of those Algebra and Geometry textbooks handy to refresh my memory.

Instant "Parkerizing"

Here is a quick and easy little tech tip for those of you who have early bikes that use a lot of Parkerized parts. As you probably know, Parkerizing is a process that protects metal parts from corrosion, leaving them with a dark gray appearance. It was widely used through the 1940's on Harleys, especially on hardware. While it is not a complicated process to perform, and there are kits available for the do-it-yourself-er, there comes a time in every restoration when you realize that you forgot to get that one bolt Parkerized.

Rather than getting the Parkerizing solution out and tricking the wife into leaving the house for an hour so that you can use her kitchen stove to bring it up to temperature, you can always use the handyman's secret weapon. No, wait ....that's duct tape. OK - the restorer's secret weapon; instant gun blue.

All you need is a bottle of instant gun blue, and your part. For best results the part will have been cleaned by glass beading (just as if it was to be Parkerized). Dip the part in the bottle for a few seconds, rinse, oil the part and you are done. Turns a half hour project for one bolt into a minute or less. I like to use a mechanic's magnet to hold the bolt, though a wire would work fine. Automatic Transmission Fluid is a great deacidifying oil to finish the bolt with. The finished product is virtually indistinguishable from Parkerizing.

The bottle of instant blue in the before and after pictures is one I picked up at Fleet Farm for under $10 this spring. I doubt that the brand matters. The last bottle I had lasted about 10 years.

The Venerable 4 Speed Clutch - Part 2

Before too much time slips away, I had better post my follow-up to The Venerable 4 Speed Clutch - Part 1 In that post I told of many of the most common problems with this clutch design which Harley used from 1941 until 1984. As promised, I would like to now give a few tips on making it work even better than when it was new. Some of these are aimed primarily at drag racing, but many are readily adaptable to street use.

1. Starting at the back of the assembly, a 5 stud clutch hub is a worthwhile upgrade for performance use. Whether you upgrade your existing hub, or buy a new one may come down to a money issue. If you can change the studs yourself it may be cheaper to do that, but if you have to pay someone to change the studs, it may be just as cost effective to buy a new 5 stud unit.


2. Replace the "clutch hub fiber disc" with the "Nylatron" unit. In normal use, this fiber disc works as another clutch plate. That means that it is susceptible to making the clutch drag if there is insufficient release between it and the back of the clutch basket. Since this plate is behind the clutch hub bearing, it is also inordinately susceptible to grease from that bearing, further enhancing the probability it will drag. Whether the Nylatron disc was designed this way or not, what I like to do is treat it like a bearing rather than a clutch plate. I grease up the Nylatron disc on both sides to make it unlikely to give any drag. An added bonus to the Nylatron is that it is "full floating", so you don't have to worry about riveting it in like the stock disc.



3. Next, in place of the stock clutch hub bearing retainer, install a "Ram Jett Retainer". I believe this little item is named after its originator, but is now being sold generically by all the major parts wholesalers. This little item is a rigid plastic/nylon disc that goes on after the basket is installed on the hub. It is installed with snap rings in place of the stock "spring clips". Depending on the indexing of the disc, it will give more or less end play to the clutch basket. Remember what I said about the Nylatron disc being used to make the assembly like a bearing rather than another clutch plate? The Ram Jett Retainer forms the other end of this "bearing assembly" and controls the end play. Controlling the end play eliminates the basket from "walking out" and causing clutch drag



4. Clutch plates. Besides making sure that the plates are in good shape (not oil soaked or glazed) the other consideration is what use the clutch will be put to. For even hard street use, I would still recommend cheap replacement fiber discs. I remember (from back in the old days) one particularly successful street class racer used a particular brand of cheap aftermarket fibers with great success. Due to having a high horsepower motor along with a street tire, he slipped his clutch while launching the bike, managing a near perfect blend of RPM and traction. Sort of like a slipper clutch, only with the rider's clutch hand providing the magic. After every pass, he would swap the clutch plates out, allowing the most recently run ones to cool. I wish I could remember what brand plates he said he ran, because he did say not all of them worked equally well.
   
   
5. Working our way out, an aluminum pressure plate will almost always work better than the original stamped steel one. They don't flex. They are also surprisingly affordable.



6. The -41 clutch springs will give more pressure than the later hand clutch versions. Keep in mind that this will make your lever pull a little heavier though (that is why they changed them when they eliminated the mousetrap; also known as a hand clutch booster)



7. The clutch spring retainer is the steel disc at the outer end of the clutch that the 5 nuts (now that you upgraded from a 3 stud hub) tighten. It will have 5 "nubs" that the special nuts index on. You're going to want to grind those nubs off. Discard the special nuts and use nylock nuts in their place. Now you will be able to get a fine adjustment on the pressure plate rather than in 1/2 turn increments as the special nuts provide.
8. Now if your bike is going to be used mostly on the street, and you have no clutch drag, you are all done. If, however, this clutch is going to see some major drag racing use, you might want to keep reading. Most clutch problems on the drag strip are related to dragging, not slipping. Even a clutch with perfect street manners will tend to drag when your bike is staged and at 4000 RPM or more. Remember, all the clutch needs to do is "pull" your bike an inch or two and you have red lighted. Besides, it is pretty much impossible to cut a good light when distracted by a dragging clutch. The solution (if you have addressed all of the items here and in the first post) is to add more release travel. As I mentioned in part 1, you can remove the hand grip to allow the clutch lever to move farther. A layer of electrical tape will make the bar a little less slippery without a grip. One last trick. You can also add a little more travel to the clutch release by shortening the release arm (the lever that comes off the top of the kicker cover). You should be able to take about an inch out of the center of this arm without adding too much misalignment to the cable. Remember, this will also make for a heavier lever pull.

There you have it! All the tricks and tips that I know for the 4 speed clutch... well, at least all of them I remember. Will this solve all of your clutch problems on the street? I think so. On the strip? To a point. Even with a more modern clutch, I found that a 6000+ RPM launch required a line lock on the front brake to avoid being pulled through the lights. But for a 60 year old clutch design, I think you'd have to agree it was a good one.

The Venerable 4 Speed Clutch - Part 1

Harley Davidson used the same clutch on all of it's Big Twin models from 1941 to 1984, with only a few changes. These days it is commonly referred to as a 4 speed clutch even though it continued in use on the early 5 speed transmissions. These days it is commonly renounced as being a piece of junk. I am sure that helps to sell more modern clutch conversions, but the clutch itself hardly deserves the assessment.



The complaints generally go something like this: "The bike still tries to creep forward even with the clutch lever pulled all the way in." The clutch is grabby." "It's hard to get into first gear." "It's hard to find neutral."



A few items are all it generally takes to make the clutch work "as good as new." A few more trick can make it better than new.



Here are some common problems and solutions.

1. Oil soaked and gummy fiber plates - solution: replace the discs. There have been a lot of "stop gap" measures to avoid replacing the fibers over the years such as baking to draw the oil out, spraying with brake cleaner and such. None of the work particularly well. Buy even the cheapest replacement fibers you can get, and you will be much more satisfied.



2. Glazed fiber plates - solution: same as above, replace the discs. A stop gap measure is to "rough up" the surface, usually by rubbing them on some concrete



3. Primary chain or belt misaligned - solution: align. If your clutch basket is inboard in relation to the engine sprocket, when you pull in the clutch, the basket will naturally move out to align with the engine sprocket. This takes up the free space between the plates that pulling in the clutch was supposed to give, resulting in a dragging clutch.



4. Primary chain or belt too tight - solution: adjust. Very similar to number 3 above. Obviously adjusting a chain is pretty easy. Some belt drives are non adjustable due to rigid primary housings. Consult the manufacturer as to why his product doesn't fit correctly. I am sure he will tell you that it is the first time he has heard of this problem. Then switch to a chain.



5. Clutch hub studs grooved - solution: replace the studs or the clutch hub assembly. This manifests itself in a dragging clutch due to the fiber discs (which have the small holes that the studs go through) being hindered from moving due to the grooves. If you choose to repair this by replacing studs, you can convert it to a 5 stud at the same time. The only advantage to a 5 stud is that allows a finer adjustment for the springs.



6. Clutch basket dogs grooved - solution: replace dogs or basket.This is similar to #5 above, except that it is the steel plates that have worn grooves into the dog s on the basket. This is far less common than grooved studs.



7. Clutch pressure plate warped -solution: replace. If the pressure plate is not flat, it will be very difficult to adjust the clutch so that the plate releases evenly. The best solution to this is to upgrade to an aftermarket aluminum pressure plate, often referred to as a precision pressure plate.



8. Clutch springs out of adjustment - solution: adjust. This can show up in a couple of ways. Springs that are not adjusted with enough tension can slip. Springs that are adjusted too tightly may coilbind before there has been enough movement of the pressure plate to allow full disengagement. The most prevalent problem, though, is not adjusting the springs for even pressure. This can cause the cause the clutch to be grabby or to drag. Your service manual tells you to adjust the three nuts on the clutch hub studs so that there is 1 inch between the stock pressure plate and the inside of the spring retainer. That is a good starting point, but for best results you need to pull in the clutch while watching the pressure plate and adjust those nuts so that the pressure plate comes out evenly. In other words, if one side of the plate starts to move before the other, adjust the nut on that side in a half turn or two until the pressure plate comes out evenly. Turn the pressure plate to different points in its rotation and double check this release. This is a major cause of a grabby clutch, and is easy to remedy!



9. Clutch pushrod and adjusting screw not having "squared off" ends - solution: machine them or replace them. This fits hand in hand with #8 above. Somewhere along the line, someone came up with the bright idea of making a clutch adjusting screw (the screw that goes into the center of the pressure plate) with a ball bearing in the end. Obviously they thought this would be a plus if you did not adjust the clutch with enough free play. The problem is that it aggravates the problem of the pressure plate not releasing evenly as described above. Picture the difference between balancing a 5 gallon pail on top of another 5 gallon pail (with lid). Now picture balancing the 5 gallon pail on a basketball. Any small difference in spring pressure from one side of the pressure plate to the other will be magnified by "balancing it on an adjusting screw with a ball on the end of it. Usually the pushrod itself will have an end that is already "squared off."



10. Insufficient travel of pressure plate for full disengagement. solution: restore full travel. This can be as simple as adjusting the clutch free play. Obviously if your clutch lever moves an excess amount before it starts to move the pressure plate, it may hit its full travel before the pressure plate has moved far enough to fully disengage the clutch. It is best to unhook the clutch cable, and then adjust the screw in the center of the pressure plate. In most cases this can be accomplished by turning the screw in until it lightly bottoms, and then back off a quarter turn. Then go back, hook the cable up, and adjust the free play at the lever. You must leave some free play or the throw out bearing will burn up. This is all it should take if all else is in good stock working order. There are a couple of other possible issues though. One is if you have a set of the really thick aftermarket grips that are on the market today. Your clutch lever will bottom out on this grip before it traveled as far as it would with the stock grip. (when I drag raced, I wouldn't run any grip at all on the clutch side just to add a little more travel) Another potential problem is in some of the clutch cables I have seen. In an effort to make clutch cables more "flexible" some of them have been "woven" with wires that are not stiff enough. I have seen cables that actually stretch somewhat as the lever is pulled, and then relax again when the lever is released. Sort of like using a big spring to release your clutch.

Well, that pretty much covers the common causes and solutions for the 4 speed clutch problems, at least those that have come to mind. I may remember more later. In a future post I intend to cover some tricks and tips for high performance use. All in all, great performance can be realized without resorting to replacement of this durable clutch with one of a different design.

(note: I tried both the "numbered list" function, as well as the "bulleted list" function and they both change to the goofy flower when I publish the post. Maybe I should add "Blogger" to my book of shame.)

Measuring Compression Ratios

Have you ever considered what the actual compression ratio of your motor is? Are you sure that you took everything in to account or are you going by the rated compression ratio of your pistons?

The simplest way to measure the actual compression ratio of your engine is to have it assembled, at TDC, and then "oil out" (old school term for measuring the volume) the combustion chamber. But to do this you must also be able to position the engine so that the spark plug hole is at the very top of the chamber so that you don't get an air bubble trapped which would throw off the measurement. Pretty awkward to say the least!

Every other method involves measuring separate components and calculating the ratio mathematically. Here are a couple of things to consider when doing so.

• cc of a cylinder = diameter x diameter x 12.87 x height

This formula is especially handy for an old time Harley guy like me since you enter the specs in inches, and the constant (12.87) converts the answer to cubic centimeters.

• Head Volume

The normal way to cc a Shovel, Pan or Knuck head is to place a piece of Plexiglas with a small fill hole across the gasket surface. When you do this you will be measuring not only the chamber, but also the space into which the fire ring on the cylinder fits. That means that the volume that the fire ring displaces must be calculated and subtracted from the head volume. Treat the fire ring as a cylinder and use the formula above. To get the cc's of the fire ring it is only necessary to calculate once using the o.d. of the fire ring and then subtract the volume found using the i.d.

• Gasket thickness & gasket bore diameter

Think of it like another really short cylinder and use the above formula to compute the volume.

• Piston deck height

If your piston only comes within .010 of the top of the cylinder, it is just like running a .010 thicker gasket.

• Piston dome volume

This can often be found in manufacturers specs, but not always. You can grease the piston rings, install the piston into the cylinder so that the top of the dome is just below the cylinder top, and then measure the distance down to the deck of the piston. This will serve as the height inserted into our magic formula above, which allows you to use the bore diameter to compute the volume of the cylinder formed from the piston deck to the top (if it did not have a dome in it). Once you have that volume you can oil it out and subtract to get the dome volume.

• Valve stem protrusion

How far the valves were sunk into the heads from previous valve jobs. Now, if you just finished oiling out your heads, this is of no consequence in computing your actual compression ratio. But it will help explain why your compression ratio is not as high as your piston manufacturer claims. Low and behold our handy dandy little formula comes to the rescue again. If you use the valve diameter in the formula along with the amount that the valve is sunk deeper than the minimum spec as the height, you might be surprised how much compression ratio you loose.

[as an example, stock size valves in a Shovelhead when sunk .050" will increase the combustion chamber size by 4.39cc, lowering the compression ratio by about 1/3 of a point]

This is especially relevant on the older motors which usually have a lot of valve stem protrusion and the valve un-shrouding which often accompanies it. In performance applications, the valves often have to be sunk to maintain valve to valve clearance with the hotter cams that are available, so that is also something to take into account when selecting your cam and pistons.

Now perhaps you think all of this doesn't much matter on your average cruiser. Well, maybe. On the other hand, keep in mind that higher compression ratios make a more efficient engine, and thus better fuel economy and power. On the other hand too high a ratio can lead to hard starting and worse yet, pinging. Another consideration is that all cams have a compression ratio range that they will work the best in.

Book of Shame

This will be a bit of a rant, I am afraid.

About a week ago I decided to start keeping a record of parts made for Harley Davidson motorcycles that don't fit, don't work and or are just plain shoddy. Believe me (and I am sure you do if you have ever worked on Harleys for a living) this is a constant, ongoing problem in this business. Lately I have had an absolute rash of junk parts to deal with.

I have dedicated a 3 ring binder to this purpose and intend to keep a record of every part I come across that is manufactured incorrectly with the part number, application and manufacturer of the "junk part."

It was really easy to fill up about 3 pages without going very far back in time. I am sure more of the parts I have "beat my head against the wall" about over the years will come to mind and be added as time goes on.

Yesterday I had a four new entries for the book which cost me about a half a day of labor. These were parts that I paid good money for, which were incorrectly manufactured. And this was all just in one section of one motor. Usually the problem does not become evident until you are in the middle of an operation. Did I mention how frustrating this can be? Then to top it off, there are always the added problems. How many hoops will I have to jump through to return the part? Is every one of this particular part from this manufacturer defective? Is there any other source for the part? Can I make the part work with modification? How much time will I waste trying to get any kind of answer from the manufacturer? Does the manufacturer care even a little bit that they are selling junk?

Yeah, a bit of a rant, but you should hear me when the circumstances are fresh. By the way, I titled the 3 ring binder "Book of Shame"

What You Pay For

I had been playing around (in my head) with a new slogan to use in my shop. Its based on the old saying "you get what you pay for". Obviously that works to use with persons who think my prices are too high. But, I think there is a danger in having my prices too low (besides not making a living). That would be the perception that if my prices are too low, my workmanship may not be as good as could be obtained at a higher priced shop.

A good example is the "Bare Bones" porting job I offer for Twin Cams. At $499, it is one of the best performance buys on the market for Harleys. When I developed this porting job, it offered outstanding flow for a very reasonable price. With the addition of the knowledge I gained during my week of school with Joe Mondello, they are probably some of the best heads available anywhere for any price! But that still doesn't stop some customers from wanting to upgrade to a more expensive porting job, even though they may not really be in the market for the higher performance potential that the more expensive porting job makes possible.

But now I have seen the other side of the coin. I recently had the displeasure of disassembling a Knucklehead engine that had been "rebuilt/restored" elsewhere. This engine had not been run since its "rebuild", so all of the sins of the rebuilder were plain to see. Though I have never met the person who performed this "restoration", it still nearly made me sick to my stomach to see his workmanship. If there ever was a case of not getting what you payed for, this was it!

Upon pulling the heads, the first problem was apparent. Rust pits in the fresh bore. I am willing to give the benefit of the doubt on this one. Maybe the oil consumption would not be too bad, and perhaps one could justify leaving the bore as small as possible, since it is for a restoration. Yeah, I'd be willing to give him that one, if that was the only thing I found. Pulling the cam cover, though, really told the story. The pinion shaft looked as though it had spent 50 years laying in a swamp before being bead blasted and then sanded. The shaft had deep rust pits over the entire surface. There was a good .002" wear on the end of the shaft that fits in the cam cover pinion bushing. That combined with a pinion bushing that had never been replaced (this was a 1938 engine) came to a grand total of .009" clearance. The factory service manual calls for .0005" (half a thou) to .0012" for that bushing clearance. Nearly 9 times too big!





Bushing end of pinion shaft

Splitting the cases revealed that the roller bearing surface of the pinion shaft was just as rust pitted as the rest of the shaft. It may have lasted a few hundred miles before disintegrating, but other things would have prevented the engine from ever running that long.

Roller bearing surface of pinion shaft

The cam was in similar shape. Lots of pitting on the cam lobes, along with .009" bushing clearance on one end and .006" on the other. Pulling the oil pump revealed a decent body and gears, but a pressure relief spring that may have come out of a ball point pen rather than the correct one. The check valve spring looked to be 70 years old, and in case it never dawned on you, springs do tend to loose some pressure with time.

About the only clearance that I found that was not way too big, was the valve to guide. And that was way too small! All four valves were fit at .001 clearance. Now, with the huge pinion bushing clearance and the way too weak pressure relief spring, there is no chance that the oil pump could have built enough pressure to get any oil to the heads, so the valves would have stuck anyway. However, at .001" valve to guide clearance on a Knuckle, it would not have mattered if the valves were submerged in oil, they would have stuck!

And then there are the rocker arms. New standard shafts in worn out rocker arm bores. One of the rockers is worn so badly that a +.010 shaft will not save it. That and rocker pads that show 70 years worth of grooving.







Wear on rocker pad

Like I said, it is enough to make me sick to my stomach. Work like this goes far beyond incompetent. Its is down right theft to charge any amount of money for this type of work!

You get what you pay for. Well, that is not always true. The person who did this to this engine proves that sometimes, no matter how low the price, you will not get any value for your money. I try to be at the opposite end of the spectrum. I do my very best to give the customer his money's worth and more no matter how high (or low) the price.

Cheap Rocker Arm Bushing Tool

Here's a quick and easy tip for you. This is the quickest and easiest way to remove the bushings from Shovelhead, Evolution or Twin Cam rocker arms that I have found. It is the tap from a kit by Colony for installing an oversize timing plug. The Colony part number is 7502-2 (which includes the tap and the plug). Thread is 9/16-18 List price is $36.64 (V Twin stocks the Colony parts under the Colony part number, but for more money)

If you have been working on Harleys as long as I have, you may already have one of these laying in the junk drawer of your tool box.

Simply use a ratchet with socket to screw the tool into the bushing and then drive it out from the other side with a punch (note the mushroomed end) I have been using the same one for over 15 years with great results. A normal tap might work, but will not be as easy to start straight and will likely shatter after a few times hitting it with a punch.

Flat Track and Old Iron

Last fall a long time local flat track racer by the name of Billy Hofmeister approached me about doing some work on his iron XL heads and cylinders. Since I have recently seen a resurgence in interest in porting work on these heads, and have done a few sets in the last year, I agreed to take a look at his heads.

His bike is an original factory XLR which is now outfitted with a 1969 XLCH 900 which he runs in local races in the open class. Last time out he had a cylinder break at the base, possibly because it had been shortened in an effort to raise the compression. Another used set of cylinders was in order, as well as some headwork.

The heads he had been running had been ported previously, but without benefit of a flowbench. They flowed about as good as can be expected with no way to check the work. Over the winter, as time allowed, I installed 2" intakes and 1 3/4" exhaust valves and a full porting job. Along with the head work, I found a set of 11.0:1 compression pistons.

Nothing too exciting here, you might be thinking; and I would agree, but what may be more interesting is the coatings we will be using. Cast iron does a great job of holding heat. Just what you don't really need in an air cooled engine. It tends to lead to all kinds of annoying little things like seized pistons and valves and such. One way of combating this heat build up is by the use of thermal coatings on the engine parts. While this technology is not new (I recall that the fuel class bikes were using them 15+ years ago) I have not seen or heard much about it in regards to antique motors.

Seems like a natural, but truth be told, I may not have thought of it except for Joe, one of my customers for whom I recently finished a big twin Flathead stroker build. He had done research on coatings and had many of his engine components done. The whole idea behind ceramic coating is to put a heat barrier on the part to prevent combustion heat from "soaking" into the part. On his Flathead, we had the combustion chambers in the heads, the combustion chambers in the cylinders, the combustion chamber side of all 4 valves, the "back" side of the exhaust valves, and the exhaust ports ceramic coated. In other words, everything that is exposed to combustion temperatures. We also had the a teflon treatment done to the piston skirts.

Unfortunately, due to some issues with the company that did the coatings on his motor, (horrible packaging for the return trip leading to broken fins along with coating the wrong ports) I was not about to entrust any parts to them. Luckily there was a local alternative. I have been having piston skirts teflon coated by a local business for a number of years. When I asked him about ceramic coatings, he said he had done some a few years ago, and would order some fresh materials if I was interested. I was.

So with the start of the racing season only a week away for Billy, I needed to get his motor wrapped up. Last Saturday I had Billy drop off the bike so I could do a "mock up" with clay to make sure there were no valve to valve or valve to piston issues. Just a very small amount needed to be removed from the intake pockets to give a little more radial clearance for the larger valves. Thursday morning I dropped off the pistons, heads and valves for teflon on the skirts and ceramic in the combustion chambers, exhaust ports and valves. Friday morning I picked up the finished pieces and started assembly. New high performance valve springs from Kibblewhite were in order, since with the porting work, the engine should want to rev higher.

So as of this writing the bike sets on a lift in my shop with just the carb left to install. I, for one, am pretty anxious to see how much the performance is improved with the increased airflow, higher compression, and a cooler running engine!

Mystery Revealed

I am sorely tempted to save this title for a post concerning theology, but it fits very well here also. The mystery that I am going to address is a damage that most will not have ever encountered, but if you have run in to it before, this will be helpful. I have been working on Harleys professionally for over 25 years, and only come across it a few times. The cause of the damage remained a mystery until quite a few years after first encountering it.

The mystery of which I speak is the unexplained "melted" piston pin boss. The initial symptom will suggest a wrist pin keeper that has come out. The cylinder will be destroyed from the wrist pin coming out and gouging the cylinder wall. Once disassembled though, things look a little less straight forward.

Instead of the wrist pin bore in the piston being intact for the most part, with perhaps some damage to the keeper groove, the spot where the keeper groove would have been looks for all the world like it was melted. This may be on only one end of the wrist pin bore, but more likely will be on both.

There will be no sign of heat discoloration, but it will appear as if the ends of the wrist pin bore in the pistons has melted away. This "melting" does not extend to the top of the piston, which rules out the melting originating in the combustion chamber. The first time I saw it, the word "erosion" immediately came to mind. At the time (mid 1980's), I was employed in a Harley Davidson dealership and had the luxury of calling the factory for technical help. Since the piston was from a recently "out of warranty" evolution, it was important to find an answer to what the cause was.

The tech rep at the factory who I talked with did not sound surprised by my description of the problem, but he dodged my question as to what had caused it. His solution was to replace both the piston and cylinder. Since the rep authorized extending the customer's warranty coverage to pay for this repair, both the customer and the dealership were satisfied. I, on the other hand, felt quite unsatisfied with this "solution" since I really didn't know if the origin of the problem had been addressed.

As a side note, the "non answer" from the Harley tech rep, reminds me much of the way the factory writes their service manuals. They will often state that "such and such" procedure MUST be done in "such and such" fashion. I for one find it much easier to remember the correct way to do something if I understand why it needs to be in a certain fashion. Most often the factory service manuals will give dire warnings about performing a task in a certain manner with no reasoning offered to support their "command". Sometimes the reasoning behind their procedure is sound, other times it is of no consequence and only added because they assume all Harley technicians are idiots!

Sorry for that rant, now back to the mystery. It was not until quite a few years later that I ran into this mystery again. The second time, the victim was a Shovelhead, and it was on a generic aftermarket piston. By this time I was working for one of the larger "unauthorized" Harley shops in this area, and so did not have access to the factory tech reps. This time I called a couple of the industry sources for pistons to see if anyone could tell me what this weird looking destruction was caused by. No one seemed to know, although Ron Dicky from Axtell came the closest when he said that it wasn't anything inherent in the piston that had caused the problem.

Since the original engine that had this problem at the Harley dealership had not failed again, I felt a little better this time about merely replacing the cylinder and piston, but the cause still remained unknown.

Again a few years passed, but then, mostly by chance, I found my answer! I was getting ready to final assemble a top end on a Shovelhead motor, when I happened to look through the end of a brand new, and just washed wrist pin. There to my surprise was a "gob" of metal filings. Have you ever seen how the metal filing that come off of a bench grinder can sometimes stick together because they were so hot when they landed that they kind of "fused" together? That is what was on the inside of this wrist pin! Just washing the pin in the parts washer and then rinsing with water had not budged the filings. I had to give the mass a tap with a screwdriver to knock them loose. There may have been about a 1/2 teaspoon in all, and once loose from the inside of the wrist pin the "gob" easily broke apart! Now it all made sense! The filings had obviously found their way into the wrist pin bore during the manufacturing process, only to come loose once the engine was running. Just add oil to the filings to help them slosh around and it is no wonder that the results looked so much like soil erosion!

Since that time I have heard of one more case of this same type of damage. I had a local "shade tree Harley mechanic" call me a few years back describing an identical problem on a bike he was working on for someone, and asking if I might know what caused it. I offered the story of what I had seen, and my conclusion, which he promptly rejected. (But then, of the half dozen times he has called me over the years with questions, he has always rejected my input, which really makes me wonder why he ever bothers to ask. When I have a problem I don't have a solution for, I don't call someone whose opinions I don't respect. There, done with that one last rant!)

I will let you be the judge as to whether or not you think I have solved the mystery of the melting piston pin boss or not, but as for me, I try to visually inspect the bore on every wrist pin that I install!

Look Sharp

This post has to do with some of the details that can make or break an engine. Sharp edges. Rarely, if ever, are sharp edges a good thing inside your motor. Of course the time to address this issue is during the engine build. I wouldn't tear down an engine just to look for a "potential" problem like this unless I had a pretty good idea that the problem is likely to be there.

Starting in the middle (more or less) we find the most obvious and in many ways most egregious offenders. That would be the pistons. It is common knowledge that sharp edges in the combustion chamber are a good source of pre-ignition. The piston domes are one of the areas that nearly always needs some attention. Many pistons come out of the box with sharp machined edges, particularly on the edges of the valve reliefs. A few years back one of the aftermarket Harley engine manufacturers even came out with instructions that if the engine was to be used in hot climates that these edges should be rounded to help prevent pinging. All that is really needed is a some medium grit sandpaper to solve this potential problem. I usually use either a de-burring tool (or Buck knife if the de-burring tool is on the other end of the shop) and then finish with sandcloth. So now your beautiful shiny machined pistons domes aren't quite as photogenic, but they are more functionally attractive. Even the generic cast pistons we use in our Knucks, Pans, and Shovels should be inspected. Often they will have a small raised spot at the tip of the dome that has a sharp edge.

But you are not done with the piston yet! Now look at the bottom edge of the skirt. There should be a slight bevel on that lower edge. If there isn't one, imagine that piston on its downstroke with just a little cocking of the piston on the wrist pin. Yeah, I can picture the sharp leading edge of that piston scraping all of the oil right off the cylinder wall! By the way, credit for that tip goes to Axtell Sales in Des Moines (the people who are famous for their drag racing cylinders), who have a note in one of their piston instruction sheets to that effect. While you are in the area, make sure that any reliefs in the cylinder spigot have a rounded edge for the same reasons. If you have added the reliefs for a stroker motor, be sure you don't leave them sharp. Aftermarket cylinders will likely come with sharp edges here. Stock cylinders are usually ok from the factory but what about after you bore them a few times?

Working our way down the engine, the outside edges of the female connecting rod where they come into contact with the flywheel trust washers should be inspected. If you are running an early roller bearing Pan or Knuckle, then attention should be paid to the edges of the case races as well as the flywheel end play adjusting washers. In the same vein, take a close look at those case races. I have seen some new ones that were rough enough on the inner end that they would work like a grinding wheel on the end play washers. Within a couple thousand miles you will have double (or more) the end play that you set it up with!

Moving over to the gearcase, some of the aftermarket tappets (lifters) that I have seen have such sharp edges that you are in danger of cutting yourself just handling them! Obviously with the designed-in side loading on these parts in most of Harley's engine layouts, what I said about sharp edges on the lower edges of piston skirts also applies to both the top and bottom edges of the tappets.

Back up top, everything that I said about the piston domes in regards to pre-ignition also applies to the combustion chamber.

You're probably starting to get the idea by now. Just examine each part before you install it, and consider how any sharp edges you find might effect the engine. Remember, look sharp . . . but don't leave it sharp. A happy Harley engine is one that looks sharp on the outside, but isn't sharp on the inside.