I have a 98 polaris 400l sport and this weekend when i went hunting. it was kinda cold around 30 degrees in the a.m. and when i went to start it i hade the choke open all of the way and it backfired. i tried it again and it started fine i ran it and it ran good. then later that day when the engine cooled down i started it again and it backfired again. it also backfired when i slow down almost to a stop and was at a idle it backfied once. does it do this because there was too much fuel in the carb or do i have a bigger problem.

 

It may be caused by a lean fuel air mixture try going up in jet sise i need to run a 250 in a stock 400 for winter. Is you etc switch adjusted correctly?

 

It is very likely the problem is related to the switch in the throttle housing . Check its operation , and the conditon of the throttle cable as well as the freeplay adjustment.

 

Also ck to make sure no mud or sticks are binding
the linkage around the carb.

TRUCK

 

My brother-in-law had a new Magnum 500 that was doing that & it had something to do with the ETC switch in the throttle housing. You might be able to cure it by tightening up the throttle caboe. Worked for him, but he went too far because when he would turn the bars way to lock, it would open the throttle a little. Loosened it back & hair & no troubles since.
Farmr

 

Carbarator needs rejeted or new spark plug