clutch spacing

There seems to be a wide range of spacing of the clutch basket on the main shaft. Often its around .040 but twice now I've come up with almost 1/4" spacing necessary to make the two sprockets align. Everything else is correct but there is this wide range here that seems excessive even taking in the year these were made. It is very strange that there is this much difference and I would like to have the clutch riding on as much on the splines as possible. Yes, I have the 3/16 spacer in the top trans mount. It could be corrected by milling off some material from the left side of the gearbox mounts which would be required if the bike was being raced. For average use it still makes me nervous. Here's a clue...It originally had a standard commando GB. I had to space out the clutch basket approx. 1/4". A few years later an LOL t-boned the bike and rider, fortunately it was well insured. New frame from Andover (another can of worms). The owner decided to install a 4-speed TTI box which took us plenty of time to install. I assumed the strange and excessive spacing needed on the clutch was a thing of the past. Wrong. Can anyone figure this out? Is it the basket itself or the clutch center machined differently? These are stock Norton parts and been there for the life of the bike. Have any of you noticed a variation in the clutch centers that could account for this? I would need several clutch centers in front of me to compare and measure.

Could be the engine sprocket going on more or less. A tiny change in the taper can make a difference.

I am very careful about the engine sprocket. I put the sprocket on WITHOUT the woodruff key and measure the distance to the motor. Then, when I install the sprockets and chain I make sure I get the same figure.

seattle##gs said:

I am very careful about the engine sprocket. I put the sprocket on WITHOUT the woodruff key and measure the distance to the motor. Then, when I install the sprockets and chain I make sure I get the same figure.

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Yes, but the distance to the motor can change from sprocket to sprocket/crank to crank/prior gorilla over tightening/someone prior lapping in the sprocket/crank, etc. Not sure what the key has to do with it?

You have just thrown in a bunch of variables. I could hope for some degree of precision? The taper is ground in exactly the same spot crank after crank after crank? Taper in the sprocket exactly the same sprocket after sprocket after sprocket? Please?
I can offer another clue...the crank is from Steve Maney, perhaps the taper is more outboard than normal?
As for the key...it can get shifted slightly to the rear in its keyway when installing the sprocket. Sometimes very hard to spot.

seattle##gs said:

You have just thrown in a bunch of variables. I could hope for some degree of precision? The taper is ground in exactly the same spot crank after crank after crank? Taper in the sprocket exactly the same sprocket after sprocket after sprocket? Please?
I can offer another clue...the crank is from Steve Maney, perhaps the taper is more outboard than normal?
As for the key...it can get shifted slightly to the rear in its keyway when installing the sprocket. Sometimes very hard to spot.

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If you search here you'll find thread about people lapping the crank and sprocket. A new(er) Manley crank is surely slightly different from a 50 year old crank. It only takes thousands of an inch to change the engagement of tapers. Some of our machinists can educate us on that.

AFAIK, if you had a fully dialed in, non-worn lathe, with one operator who was not in a hurry and the sprockets were already made perfectly and each crank and sprocket was hand fitted, you could have the precision you want. What you really have is closed enough precision and shims to align the clutch with the sprocket.

I recently watched a video where a person was making a specialized tool with Morris taper to fit the tailstock of their lathe. Thier first try was off about 1/2 degree and the engagement was crap then when they tried to correct they over did it and it went in too far.

What bothers me about the situation is that the clutch center does not have full engagement with the splines on the mainshaft. I would like as much as possible.
So, if I had 10 engine sprockets I could try each one and pick the one that sat furthest inboard.

seattle##gs said:

What bothers me about the situation is that the clutch center does not have full engagement with the splines on the mainshaft. I would like as much as possible.
So, if I had 10 engine sprockets I could try each one and pick the one that sat furthest inboard.

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You could.

Be positive that there are no burrs on the crank or in the sprocket.

Be sure you're NOT measuring from the inner primary to align the sprocket and clutch.

Make sure your engine and gearbox are tightened and in proper alignment.

Realize that the clutch basket is wobbly when no plates are installed so it's easy to think you are or are not aligned. Try putting the clutch fully together with no shims, and the sprocket at least tight, and measure how much you are off, and add the required shims.

You could lap the sprocket/crank, but I would think long and hard before I did that and it would be a tiny bit at a time if I did.