Vintage Dirt Bike Q & A

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PostPosted: Wed Jun 03, 2015 4:44 am 
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Joined: Mon Jun 01, 2015 3:33 am
Posts: 2
Hi all

I have just joined - I'm part way through rebuilding a 1982 CR125, which I got off ebay last year - see picture. Quite a few bits were missing (and some, like half the crank case are from a 1981 bike), but I'm slowly working my way through it all.

My biggest issue is that the engine had a knackered crank shaft and no primary gear/water pump gear. I have since bought a replacement crankshaft and the gearing, but I'm having real trouble with the the collar that fits under the primary gear on the crank shaft - see photo (BTW - the crankcases are not together in the photo so the crank shaft will stick through more when they are - don't want to join them until I have the collar issue sorted out - in case I have to change the crank).

I have ended up buying more than one example as I cannot yet find a collar that fits over the end of the crank. The only one that does is one from a 1978 CR125, which slips over nicely, but isn't as deep as it needs to be - see photo comparing the two collars - the 1978 one is on the right.

I appreciate that the collar should be relatively tight on the shaft, but the ones I have which purport to be from a 1982 model would require extreme hammering to make them slide down the crank - and that can't be right? Of course maybe I don't have a 1982 crank, but it looks the same as the knackered one that was in there - are there subtle differences in the crank shaft diameter between models? I would say that I need another 1 mm of inner diameter on my collar to get it to fit - the diameter of the current collar being 20 mm.

All advice gratefully received as this is really holding me up

cheers
Richard


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