Peter, something is wrong and I suggest you do not use the bike until it is sorted out. If that nut comes off the dynamo drive and goes through the primary chain it can break the chain and/or break a piece out of the front of the crank case and more. Two threads is not enough. Also your description of the dynamo drive sprocket does not sound right. There should not be a raised portion on either side of the central hole. The sprocket teeth themselves should run in the central line of the chain. Does yours do that? There are different drive shafts on different dynamos. Some are tapered and some are parallel. Do you have all the correct parts to mesh together?
Hi Timetraveller,and thanks for reply.
I apologise to all for being on wrong thread - I searched for Dynamo Drive, and this one came up.
Should Twin Dynamo be somewhere else?
My situation is: I fully appreciate the damage that loose metal in primary chaincase would cause, hence my concern.
I have "C" Rapide, and the dynamo drive is as per handbook, tapered drive from armature, through dynamo drive boss, oil thrower ring, drive sprocket, drive plate.
There is only about 1/8 " of thread showing when these are in position.
My question is why, and I wonder if the PD16 drive boss (with tapered hole) may be too thick.
So I measured it, and need dimensions of a known correct PD16 to compare.
I believe the armature thread is correct length, as I have two the same.
Dynamo is Miller, the long 3" one.
The raised portions i referred to are not on the sprocket, but are on the drive boss.
In hope of a safe solution
Peter