C15 Drive Chain/ Case Clearance

[mcman56]

I'm assembling a C15 and see that the drive chain hits the inside of the engine cases. By inside, I mean the clutch side. This is a 428 chain with the smallest (13 tooth?) sprocket. I know you can run a 520 chain so something must not be correct. Can someone tell me what a notmal or expected clearance should be? A couple of pictures are attached.

[b40rt]

Its always pretty close. That looks like a heavy duty chain to me, think that's the problem.

[walworth]

Is the rear wheel too far over to the left? looking at the second pic, it looks as though the chain is not parallel to the casings.

On the first pic the chain is over to the left, closer to the frame tube than I would expect. Good luck.

[richt]

The size of a chain is measured like this:

a 520 chain is 5/8" pitch x 1/4" width of rollers

a 428 chain is 1/2" pitch x 11/32" width of rollers

The chain in the photo looks too wide for the sprockets.

Does it slide from side to side?

If your sprockets are 1/4" wide then I think you should be fitting a 420 chain which is 1/2" pitch x1/4"width

[b40rt]

Well ?

[mcman56]

I just saw this reply. The chain is an RK 428 heavy duty... maybe the "heavy duty" makes it wider?? The gearbox sprocket is a newly purchased 428. The rear wheel is from a Bultaco Alpina which I understood also used a 428 chain. I'll measure the width. I did put the original C15 wheel on and saw the same thing.

I looked closer at the frame and the rear motor mount/ swingarm mount is twisted a bit to the right and up. I have another posting with pictures on this. This sort of pulls the back of the engine to the right and into the chain. I have been pursuing straightening or replacing the frame.

[b40rt]

I just saw this reply. The chain is an RK 428 heavy duty... maybe the "heavy duty" makes it wider?? The gearbox sprocket is a newly purchased 428. The rear wheel is from a Bultaco Alpina which I understood also used a 428 chain. I'll measure the width. I did put the original C15 wheel on and saw the same thing.

I looked closer at the frame and the rear motor mount/ swingarm mount is twisted a bit to the right and up. I have another posting with pictures on this. This sort of pulls the back of the engine to the right and into the chain. I have been pursuing straightening or replacing the frame.

Heavy duty is wider, try a standard 428 before any major modifications.

[mcman56]

Based on some recommendation, I built a fixture to hold the frame on a bike carrier mounted to a trailer hitch. Using a long lever in the swingarm pivot, I tried to bend it straight but the 7/8" SS spindle on my lever just bent. I heated the short tube between the swingarm/ engine mount bracket and lower casting and was able to straighten the piece. Upon assembly, the chain/ sprocket/ case alignment looks straight ...or maybe straight enough. That heavy duty chain does make everything very tight.