If his EX is new, I'd look @ jetting first. New Hondas don't usually show those other problems. Also, jetting is a cheap fix, about $5. Good luck

 

popping on decel is almost always lean condition. Get a bigger pilot jet.

 

My 250 ex does that too and i can't figure out what it is. My uncle is a mechanic and he said it might be the jetting but i haven't messed with it.

 

Yea, what he said!

 

I agree with many people, you need to rejet. Not being picky, but the correct term is back firing. Good luck.

 

Mine does that also. Haven't messed with it. Been a trouble free quad so far. I think I'll take the carb apart and maybe change the pilot jet.

 

I cut a huge hole in my air box lid and covered it with mesh and it was running to lean and back firing alot so I put a bigger main jet in it and it now runs perfect. My stock main jet was a 145 and I changed it to a 148.

 

My 250ex popped, or back-fired when I let off the gas too. warm the engine up for 10 minutes and adjust the idle screw on the carb. if you're sitting on it, it's the screw on the carb on the right side. just try turning it back 1/4 a turn each time then take it was a short spin. just keep the screw driver in your pocket (standard) and keep adjusting it until it doesn't pop anymore. sounds like the idle is too rich.[img]i/expressions/face-icon-small-happy.gif[/img]