Sometimes that bad vibe is caused by the clutch starting to go...one of the corks rips off causing the clutch to load to oneside and become unbalanced...1st gear clutch nut likes too come loose and cause vibration too...broken "J" spring causes a bad chatter shifting from 1st to 2nd...Points is OK but at high rpm's the thing will blow light bulbs...(12v regulator?)..and you can't run the big gear...A35 cdi has been trouble free for 3 years runnin at 12,000+ rpm all the time... bolts right on PUCH's tooo