my dads bomb backfires alot and doesnt run very well, its mostly during deceleration. He has an aftermarket cdi and I was wondering if this could mess up his timing causing the plug to fire while the exhaust port is still slightly open. anyone have other ideas? I want to see the big yellow running good again.

 

I am by no means an expert on this. However I do know that incorrct pilot screw adjustment will cause backfireing on deceleration. Just open it a 1/4 turn each time until it stops backfireing. I think 4 turns out max. If your backfireing all the time as well then in could be another matter all together. May not be related. But when my valves needed adjusting mine ran like crap. And the backfireing on deceleration was there as well.

 

My ds was doing that because of an exhaust leak where the header comes out of the engine,or because half the stuffing was missing in my big gun race pipe,I fixed both so I dont know which one fixed it but it stopped backfiring after that.