3 quads i have a 03 650 that was poping and it turned out that my raer clyinder jumped time.so i retimed drove 200 miles did it again.now in the process of totla rebuild.cam chains pistons bearings. Good luck with your quad

 

i have a K&N filter on my kfx700 and it does well at filtering the dust. i ride behind my dad sometimes and it gets so dusty i can barely see. after a couple times of riding, i took the airbox lid off to clean it, and it was very dirty and dusty. i took the filter off and it looked inside of it and it looked brand new out of the box. kept my carbs nice and clean. i guess u just have to keep it oiled and have a good grease seal underneeth it.

 

There is nothing wrong with running a K&N, Twin Air or UNI. If well maintained they will work just fine.

If you are having troubles off idle to 1/4 throttle, your problem is either in your Idle Circuit (Adjust your Air Mixture Screws) or you may have a problem in your Pilot Jet (Check your Pilot Needle & Pilot Jet. Also check to make sure your Slide Spring isn't broken or a hole in the diaphragm). These can be found by removing the round black covers on your carbs. You may also have a choke sticking.

Your quad will pop on decel if your air mixture screws aren't adjusted right. A cracked or loose exhaust can also cause a pop on decel. Being too rich can cause a pop but this generally occurs a WOT.