what causes popping thru the carb?

[cals400ex]

on start up my bike pops thru the carb and it is a pain in the butt to start. i have a feeling it may be lean on the slow jet but i am not sure. it runs fine when it warms up but is tough to start and just seems to pop or backfire thru the carb. i am running a fcr 39 right now. i ordered a larger pilot jet but it isn't in yet. i have a 50 in now but i think maybe i should richen up the fuel skrew and that might help. any suggestion?

[greco400]

Mine does that too and i was told i was lean on the pilot and i richen it up and it solve it try that

greco

[cals400ex]

this is what i exactly figured. i've had a larger pilot on order for a couple weeks but it just isn't in yet. my head pipes aren't glowing at idle so i know i am not really lean but it is a PITA to start in the cold but is great when the bike is warm. thanks and other suggestions are welcome

[KY Woods Rider]

It's most commonly caused by lean jetting, although I have seen a few occurences where people flooded a quad while trying to start it and ended up causing it to spit back through the carb.

Going by the difficult cold starting, I'd say it's a fairly safe bet that you're a little lean on the pilot or screw.