Backfire through exhaust

[retrorich]

Can someone on here help with a large backfire from exhaust, once scooter is up to temp. It cuts out without warning (usually at low revs at moment) and backfires then it may start up again but the problem persists until it stalls. Kick it over and it starts first time but will backfire shortly after.

I have cleaned carb out and flow of petrol is good. The spark plug is white when I remove so running very lean..
Set up is:
Variatronic ign with mapper box
200 Mugello
26PHBH

[garry inglis]

i think i would look at ignition set up and check what your starting on and retarding too

[mick1]

Agree with above ^

Might be worth strobing the engine to see if everything is as it should be.