There are many reasons that a vehicle will backfire through the carburetor. What determines the cause depends on what condition the backfire happens. Is it a steady backfire at idle or does it start when you are accelerating ? Do you live in a wet climate or dry? Has the engine been wet?
Backfiring is caused when the exhaust valve is open during the firing or compression stroke of a certain cylinder. For example, a broken spring will not close the valve completely. A bad camshaft lobe will cause a back fire, if you have a distributor that got wet the spark could cross over to another area wire and cause the problem causing a missfire. If the wires were put on wrong after putting in plugs it will cause a missfire.
SOURCE: raptor 660 backfires and pops
Hi mate most common setting on almost all carbs would be 1.5 to 2.5 turns out. if runs better with less turns out than this range, then you need smaller pilot jet, or if needs more turns out then 2.5 you need bigger pilot jet. The glowing red header pipe is normal every yamaha I know will do this especially if left to idle for more than a minute... Regarding issue of popping this nearly always due to lean pilot circuit. first step clean pilot jet and or up size your pilot jet 2 or 3 sizes. just to clarify the turns out procedure make sure you are counting a full 360 degree turn out as 1 turn. I have seen in the past guys adjusting this air/fuel mixer and counting 180 degrees as 1 turn out needless to say it don't work... cheers mate hope it helps
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SOURCE: Changed coils on Harley now it won't start just pop or small backfire!
Please remove sparkplugs and hold them on engine connected to cable and check for blue intense spark on both plugs after that when connected and if the engine still does not start if possible please try with a new set of sparkplugs maybe that should do,all provided the coils are engine specific, wish you good luck
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