A query or two I'm hoping someone can help me with follows.
I've got a '72 Vespa Rally and recently put on a SIP road 2 exhaust and upjetted (from 107 to 112).
At first, it WAS plug and play.
Until after about 45 minutes of riding - when hitting full open throttle, engine starts to sputter in high revs particularly in 4th gear - until finally it sputters in every gear (yet is strangely okay idling with no revs for a awhile) then quits.
Let it sit and it starts and runs well for about 30-45 minutes - then the crap starts again. Finally conking out.
1. a new sparkplug that can run cooler 2. checking/removing the airfilter 3. downjetting back to 107.
Fix more than one thing at a time on these classics and you multiply problems..
I was thinking it could be heat related... or maybe the stock points of a '72 rally cant take the revs for an extended time... fried the points or the timing needs adjustment.
Any help or ideas would be appreciated. Thanks in advance!