450r backfiring
 

My 05 450r is backfiring and only getting worse. it has a full trinity stage four exhuast, it was on the quad when i bought it. How do i check to make sure its jetted properly and were can i find that its the right iet kit? It only really backfires wen i let off the gas, and it shoots out like a 6" flame out the xhuast

i would go 2 1\2 air fuel and go one size bigger pilot and main. after installed slowly rev the motor all the way the wot. if its missing in the 1\4 throttle its the pilot and if wide open throttle cuts out its the main. witch means your still to lean you need to go bigger. when adjusted the fuel screw you will need to readjust the idle do to the fact that they worked hand and hand together.

What do u mean 2 1/2 air fuel?

He means to bottom out the fuel screw(gently) then open it back up 2.5 turns. Generally, if you need more than 2.5/3 turns out, you should just go up one size on the pilot instead.

Has the quad always backfired? If it has ran fine in the past I would look for an air leak before messing with the carb. Check your intake boot for looseness or cracks, make sure the airbox lid is still ok(if you were using it before) If that checks out, look at the exhaust sideofr any leaks as well. You also COULD have a leaking headgasket.

Bi
Well at first it was popping. Then i was starting it a flame shot out and it sounded like a shotgun, but before that nothing more then usuall.

Have you checked compression? If the cylinder is wore out, it'll do what you're talking about. Just an idea.

The compression is solid u can feel it wen u kick start it , its kinda hard to do some times if it dies out while riding. THere are no leaks in the carb or boots, i was told it could b the spark plug if theres debri in there does that sound right to anyone, my airfuel screw is perfect, it idles fine then once i give it gas and let off thats when its the worst.

I am pretty sure you have too big of a jet in there. Stock is 118 or 125. Check what you have in then put in a smaller one. Run it. If it's good then your done. If not put a smaller one in. Make sure you clean your carb when you change the jetts.

Back firing and flame out the exhaust on decel/closed throttle is indicative of a lean pilot. The flame sounds counter intuitive, but that is the way it is.