More Clutch Questions

[go_hercules]

Hydraulic Jack in another thread go me to thinking about why I need so many shim washers under my throwout bearing. So I tore it back apart and measured everything. This is a 1973 Dirt Squirt 100. Here are all the parts and dimensions. I have nothing to compare them to so I assume they are correct. But how would I know?

The face plate has the correct part number on it (934008). I also have a spare face plate from God knows where which is about 0.075" thicker than the one shown.

From the gasket surface, the push piece dowel is at 1 11/16 inch (1.687). The push piece dowel as I call it, is 0.470 inches long.

There are 4 friction discs which measure 0.080" thick all the way across. In other words, no step where they meet the steels, virtually no wear. There are 3 steels as the parts list shows.

The spring dimensions are shown here.

With nothing to compare to, I have no way to know if all this is correct or not, unless someone happens to have some parts to measure.

[Hydraulic Jack]

I don't see anything that looks out of line. The same clutch cover plate was used in lots of different engines including the 125's. Don't know if the thicker one was perhaps from a 90 or early 100? Since the one you are using matches the parts book, I would go with that one.

Now I feel bad that you took your bike apart just because of my wondering about your shims.

My pressure piece is 0.448". The kick start rollers are the same diameter, but a bit longer at 0.468". They are not shaped the same. The pressure piece has a beveled edge on one end, and one end is clearly machined flat. The kick rollers are not quite square shouldered on both ends and don't have a machined appearance on the ends. Forty years after manufacturing, who knows.

Pressure piece on left, one end ground flat

Pressure piece on left, one end beveled

I don't have an answer for you. For all I know some previous owner took it upon himself to grind a kick bearing to fit as a pressure piece in the engine I acquired. Maybe it is something else I am not seeing, like a tolerance difference in the width of your left crank bearing inner race. Please don't disassemble and measure it. Maybe you have a really thick cover gasket. I don't know. Maybe one or the other of us has one of those other thicknesses of throwout bearing Ed mentioned.

Since your clutch works, I would just use it as it is. At least you now know your clutch intimately.

Afterthought, maybe yours is the normal clutch and mine is an anomaly.

[go_hercules]

Thanks Hydraulic. Maybe someone else has some parts they can measure so we could verify what's going on for sure. From a known Dirt Squirt would be real handy.

[go_hercules]

Oh, and also you guys mentioned there were different throw out bearings, maybe three different ones. Any pictures of the differences in them, or where they were used?

[Bullfrog]

Hydraulic, your clutch pressure piece has been owner modified.

The kick rollers and the clutch pressure piece are exactly the same part (#901507 - nominally 8mm diameter by 12mm long) from the 90 thru the Model 98. The pressure piece part number changed to 991507 in the Model 99 Road Toad - but I can't tell you what changed about the part (don't have one I can get to easily for measuring).

Here are the measurements I got on an un-modified 901507: Dia. - .314" (7.97mm), length - .468" (11.9mm).

I'm pretty sure I have photos of the three "throw-out bearings" somewhere around here . . . but it will take a bit of time to find 'em - (I have another Hodaka project in progress and I'm past the deadline for getting it done, so I've got to whale on that to keep from getting myself in hot water.)
Ed

[Bill2001]

Ed, this is a problem we see in many classic/restored bikes. Parts are sometimes mixed-and-matched from whatever is onhand, or available from stock, or what was dredged up on eBay. When you go into a new-to-you bike it is a good idea to check everything. You just don't know what is there.
For example, on my Wbat, I found that the clutch assy was "new", and checking receipts it seems to be a rebuilt unit from Hodaka Parts. I'll presume it is "correct". I didn't break it down when I was in there, but when i blueprint the clutch later this year, I'll double-check.everything.

[go_hercules]

OP here: I am starting to think my clutch assembly is from an ACE 100, because the friction plate thickness and spring lengths match what is shown for that engine in my Clymer manual, rather than what is shown for the Dirt Squirt. Maybe the whole clutch was changed out a long time ago.

Also, while playing with this thing on the bench, I noticed that after smoothing the teeth in the cage with a small flat file, the steel plates can move back and forth a little. Not a lot, but enough to see and feel. How much play is too much there? I assume they can't be too tight or they would bind. Maybe a sliding fit with no wiggle sideways? I could see where a guy could go crazy smoothing out that cage and have all kinds of play if he wasn't careful.

[Hydraulic Jack]

I suspect you are right, Ed, that my pressure piece was owner modified. Given the rather short shim stack I have, I would not be surprised to find that a standard piece would require no shims at all, and might not give adequate clearance. I will play with it during reassembly and see what I get.

I notice that the pressure piece has been numbered variously over the model years: 901507, 991507; and the kick rollers also vary: 904713, 901507, and 901507A. Who knows why the numbers would change if the pieces did not. The kickmrollers I suppose I could see since I think the roller cages did change at one point, perhaps for the 125's.

I have another, older engine that I haven't taken apart yet, and I will measure the parts in that one in due course. It is a model 93, so closer to the dirt squirt in design.

Regarding putting a clutch from a different model in your bike, as far as I know they tend to interchange as an entire assembly, but might well require different shimming ranges to work, so perhaps you do have a clutch from one machine and a throwout bearing from another, and all it takes is a couple of shims to make it work.

Filing the aluminum cage always creates more clearance. Not usually a problem, just don't take it to extremes. My observation has been that the steel drive plates will always wear the aluminum cage, but that most of the binding in the clutch comes from torque shifting between the inner and outer clutch covers and the cage causing misalignment. Widening the slots in the drive plates around the screws mitigates this somewhat, but if the three clutch body parts, cage and two covers, were never free to shift, the drive plates could not touch the screws to start with and so filing out the plates would be unnecessary. Studying the wear patterns in the cage left by the plates and the screws shows that the covers do rotate on the cage just a tiny bit, both back and forth (acceleration and deceleration). Not getting the seven screws tight would make this worse, but getting them perfectly tight does not stop the shifting of the covers. I am working on a solution.

[Bill2001]

I wonder if a couple of alignment dowels could be put in the Cage and inner/outer covers to restrain that residual movement. The cage is aluminum and there is not a lot of meat, but the residual movement force is small and most of the restraint us provided by the bolts. 3/32" dowels would be more than adequate.

[Alberta Mike]

All of a sudden I'm wading into a discussion like I know what I'm talking about ..... ha! I think Jack mentioned about the gasket thickness. I have a new one here that for whatever reason came with the bike 24 years ago and I just came across it with some 0.010 shims. I didn't realize I even had them a week ago. This gasket is sort of a rubberized thick & rigid paper material whereas the one on the bike now is a rubberized cork which has compressed quite a bit thinner over the years. This thicker spare one I have isn't going to compress too much if and when I use it. No question from the discussions and what I have gleaned on the topic so far, gasket thickness would indeed be a factor.

[JackM]

Mike, I'm glad you started this topic about clutch questions because I would have been asking the same type of questions if not for following this conversation on here. Just got around to hooking the clutch cable up on my 98 project and found there was no free play at all in the side-case lever. There were four shims in mine. I took two out and voila, looks like just the right amount of freeplay. As an old RR engineer once told me when I first hired on : you learn something new every day. Its true with the railroad and true with a lot of other things as well. Thanks. JackM

[Bullfrog]

I'm going backwards through my digital photo files to search for the photo of the various Clutch Discs ("throwout bearings"). I'm back to 2013 and haven't found it yet . . . but I know it is there (somewhere).

In the mean time . . .

- Yes, filing the teeth on the inside of the clutch cage does increase rotational freeplay of the steel clutch plates within the cage, but you get smooth clutch action in return by eliminating the "wash-board" surface on the teeth. It appears to me that the primary "negative" introduced by the increased rotational freeplay of the steel clutch plates within the clutch cage is the potential for slightly accelerated return to a "wash-board" condition of the clutch cage teeth (perhaps offset by the elimination of cage gouging due to the removal of burrs from the steel plates when they are "blue printed"). NOTE: every time the clutch is used, there is a teensy bit of impact/wear which results in the "wash-board" wear pattern over time. I have not noticed a rapid return to the "wash-board" condition on the clutches I have "cleaned up" and then used on my bikes - but I KNOW it WILL happen over time.
- There is an ingenious clutch re-assembly modification which goes a looooonnnnng way to reduce "racking" of the clutch in use. In honor of its discoverer/inventor (thanks for the logical leap Phil!), I call it the "Chapman Clutch Pack". I think I have photos of that too . . . I'll add it to the search. (Hey, wait a second. Has the Chapman technique already been published in the Resonator? I'll have to check that too.)

Ed

[Alberta Mike]

Jack, we just had a visit with a friend of mine who now lives at the coast (Vancouver) ...... his dad was a CNR (Canadian National) freight train engineer all his life here in Alberta. The old man is now 87, started smoking when he was ELEVEN years old, never quit and still has 6-7 sticks every day and is definitely "a piece of work" as the saying goes. My son and I went for a ride with him back in '85 on a day run about 3 hours round trip. You don't think my kid was excited at 11 years of age riding up in the "front end" as the crew referred to the engine? And he even got to pull the cord that operated the horn, pretty cool time that was for sure. What railroad did you work for? Railways intrigue me, always have, just last month we were in Vancouver and took the Amtrak to Seattle to watch a baseball game, great train trip, first class.

[JackM]

Mike, I was an engineer for CSX for 30 yrs. Been retired for almost 10 yrs now and loving every minute of it. It was a good job, but I was glad to get away from it, especially since their new CEO is making big changes now and running it into the ground.

[go_hercules]

I am going to order a new clutch cage and other parts from Paul but I am not quite sure what I'm working with. The bike is a 73 Dirt Squirt but I think the clutch is possibly off an ACE 100. Anyway, the clutch cage is different on the two. Until I get in touch with Paul, does anyone happen to have any reference as to dimensions of these cages: 934004 (Dirt Squirt, 92B, 92B+) and 924004 (92A). I think they are different thicknesses, but maybe other differences. The cage I have is shown in the first photo above. The parts might be mixed and matched for all I know, but the cage works good in this combo, just a little worn - especially since I filed the teeth. So if I can just identify what I have I will be in business. I'm sure Paul can identify it when I talk to him, just trying to get informed. Thanks everyone.

[Hydraulic Jack]

Measure your cage, and be ready to give Paul the measurement. If he has the part in his inventory, he can measure and verify.

[go_hercules]

Yeah, that's what I will do Hydraulic. Seems like these cages are easily mixed up. Looks like the only dimension that might be different on some of these cages might be the thickness. Easy to mix up for sure. Once I get the right one from Paul I will post the thickness and part number for reference in case anyone else needs it.