Autonerdz forums

Gauto, historically not always but mostly backfires are lean burn or out of time.  In most cases not knowing here and caburburated a back fire when turning down the throttle is a lean or plugged piloit jet.  Does the bike Stumble mid range but come on strong with wide open throttle is also a clue.

You have idle cirucuit, pilot circuit which is mid range and main jet.   I would suspect a compromised pilot jet in your case usually just a cleaning issue.

Again could be speaking out of place here but sounds like a plugged pilot jet. Sometimes even have to go to the next size larger to fix the issue.

What happens here is you go into a lean burn (turning off the throttle) and although lean not as hot it takes longer to burn thus the opening of the intake valve while there is still fire in the jug now coming up through the intake, which technically is what is happening. The other scenario when this happens is the timing off, not the case here as does run good other wise.

StitchB.

James H wrote on Dec 11^th, 2016 at 5:17am:


James, yes just assumed it was a 4 stroke and we know how dangerous that can be , Assuming.  The only 2 strokes I know of as of late is the Aprillia system which works pretty well. I'm a big fan of 2 strokes just not where we are in the world today, but all good points you made, duely noted.

StitchB