my scoot has small back fireing.

[blue]

My 50 cc 4 stroke scoot is back fireing. Its not to bad more of a spit. The scoot runs to top speed and drives great.Im the typ of guy that beleaves in if is not broke don't fix it.But it been buging me lately.I checked the scoot out good and so far all is ok. New plug and wire clean carb.valves done about 3 months ago. just asking what could it be.the muffler is also tight.im thinking maybe it just needs new gas lines.maybe small air leak some wear.

[tortoise]

Verify carb air-cut-valve diaphragm is not deficient.  During deceleration vacuum via a throttle bore port retracts the diaphragm probe (compressing the spring) to close the check-valve . . which richens up the pilot port mixture slightly to avoid a lean backfire condition.

[blue]

Thanks....that I can do.Ill check it out.

[blue]

Well That's not it. My scoot has a khien carb if that helps. its a little dif. from whats in the pic above. Maybe ist the pilet jet its self ill clean the whole carb in a few days.

[blue]

OK...........the carb is clean and it still back fires.took for a test drive .and I notice that it only does it after the scoot comes to a slow down after rideing full throttle .Or in between 25 to 35 miles a hour........Not rulling out the air valve yet.It might be something I cant see.  The scoot runs very good gets up top speed like it should rides smooth sounds good. Its just the back fireing has got my mind playing tricks on me on what it might be. any ideas....