I have replaced the chain 2 times in my transmission and it keeps stretching out. I bought this machine used last year and im about to replace the chain again with a new chain. My question is about changing out bearings in the transmission. I read a few forums about replacing the pinion bearing. My bike also wines very loud. What bearing is the pinion bearing and what other bearings should I replace? I just don't want to spend $250 on bearings if I don't need to replace them all. Please help.