Originally Posted by
23skidoo
When you say 'throws the chain off the ring' do you mean it just drops the chain to a higher gear or throws it completely off freewheel and onto the hub? Could it just be a low limit adjustment problem on the RD? When you're set on big/big how do the pulley wheels line up in relation to the sprocket? They should be just slightly inboard of being centered and if they're any further you can use the low limit adjusting screw to return them to the proper alignment.
When I said the big-big combo threw the chain off the ring, I meant that the chain was being forced (inboard) off the large
front chainring. The RD limits are properly set.
My other suspicion is that the bb spindle is too long--but, man, I really don't feel like messing around trying to find a shorter spindle for these cottered cranks. I honestly don't have much experience with cottered cranks and would rather just leave well enough alone.
I'll try and take some pictures this evening.