I just got up and running and while out for the first day noticed an inordinate amount of backfires while decellerating. I have no mods but a cobra f-1 slip on canister that is said to require no adjustment to the fuel system. anyone have a clue?

why is this post in the classifieds section ?

However, check if carbs are synchronized well, valve clearance is ok, spark plugs are in good condition and with correct gap and at last.
Measure the voltage at the coils while engine is running. If it`s lower than 12V disconnect the orange leads to the coils and connect one to a relais (isolate the second end). Run a wire from the battery or starter relais (with an inline fuse) directly to the relais. Hook up a ground connection and make an Y-lead to connect the coils to the relais. Then you should have full voltage at the coils and combustion (and starting) should already approve (the orange leads will now only switch the relais). The rest is fine tuning.

Gerhard

My guess is the slip-on is leaking at the joint, or you have some other leak in the exhaust system.

It's pretty rare that a bike with an aftermarket muffler wouldn't benefit from having the carbs rejetted or injection rechipped.

desmodog is correct, i had same problem and it was air enter motor at front cylinder at loose hedder connection...try tightening hedder bolts....

Usually its caused by air leak in headers, but not allways: When i had Weber in my 750 Paso, i had very bad and big "banging", when use engine brake and also after some seconds i have turned engine off, but when i changed to 40mm Dellortos, such never happen anymore ... remembering those times, when i had big fun with my 750 Paso..... :laugh: :laugh: :laugh: So, should i have to turn back again to WEBER???