Backfire after i warm my bike up and push the choke in and when i rev it , the bike will like backfire/misfire, and if i hold the throttle steady it will backfire like 2 times again....and it does this while riding at a steady pace too...it just started it didint do it a week ago. i didnt change anything except a new air filter..fuel screw is 2.5 turns out . the timing, valve clearances and everything is in spec. is this a sympton of it being rich or lean? and it doesnt do it on choke

SOURCE: backfire

Yes, it could (and probably is) be an air leak. Check to be sure the carb is tight in the intake manifold, and make sure the hot-start isn't loose and is sealing properly. Also make sure all of the exhaust system joints are tight, an air leak in the exhaust will make a four-stroke pop and backfire like an old work truck with no muffler...

SOURCE: backfire

Yes, it could (and probably is) be an air leak. Check to be sure the carb is tight in the intake manifold, and make sure the hot-start isn't loose and is sealing properly. Also make sure all of the exhaust system joints are tight, an air leak in the exhaust will make a four-stroke pop and backfire like an old work truck with no muffler...

SOURCE: bike backfire

Yes, it could (and probably is) be an air leak. Check to be sure the carb is tight in the intake manifold, and make sure the hot-start isn't loose and is sealing properly. Also make sure all of the exhaust system joints are tight, an air leak in the exhaust will make a four-stroke pop and backfire like an old work truck with no muffler...

SOURCE: backfire

Yes, it could (and probably is) be an air leak. Check to be sure the carb is tight in the intake manifold, and make sure the hot-start isn't loose and is sealing properly. Also make sure all of the exhaust system joints are tight, an air leak in the exhaust will make a four-stroke pop and backfire like an old work truck with no muffler...

SOURCE: backfire

Anna14 is right with the air leak,this can also be a misadjusted or faulty throttle position sensor or defective CDI Unit or a lean feul mixture.