When I had rebuilt my ds 650 and got it back together it was starting to backfire but only when I was reving it at high rpm's. And my old cdi box was bad so I had put on a new stock one do you think this could be the problem or something else.
thanks Brett

 

try changing ur spark plugs

mine use to do that but after it got new plugfs she ran like a champ

 

yea I had just recently done that and gapped them to the right spec but it only seems to do it when its reving at high rpm's or when I shut her off without sitting and cooling.

 

How are your spark plug colors? nice tan, white, black? Check to see if you have any leaks in your carb boots such as intake boot, filter to carb boot. Check to see if your exhaust is leaking....check header bolts, mid pipe connection and the other connection up front. Ive never had any experience with a bad cdi so im not sure if that could be the prob...but from what ive heard a bad CDI can cause ALLOT of problems. I had a little bit of a backfire and my jetting was almost spot on, turns out my header bolts came loose a bit letting cold air in and causing a backfire.

 

A leak in the exaust will definatly cause pops and cracks out the pipe, but usually only on deceleration. This is caused because when you let off the gas, your exaust pressure drops off and causes a suction because your engine is still spinnin rpms, and therefore it will pull in fresh air through the exaust leaks and it will cause rapid burning in the exaust system and this is the excessive popping and cracking you hear out the pipe. If it is not exaust leaks, then you need to do a plug check at wide open throttle, because it may be runnin lean on the big end.

 

alright thanks alot ill make sure to check my plugs and my headers may be loose so ill make sure to check to see if they are tightened enough.Thanks again

 

I took my headers off today and found out that the gaskets were pretty much non existing so I'm going to order new gaskets and tighten her back up thanks again.