2000 artic cat 400 ,starts but when accelerated it Backfires & dies ,getting fuel to carb ok ,lines are clear ,gas tank flushed out .Is there an adjustment for carb Low and High speeds ? New to this but have mechanical background .any help welcome .

 

Did you replace the spark plug? Sometimes they short under load

 

Is has been my experience with my ATV's that when they backfire and die while either accelerating or letting off the throttle ans it was running fine then I have some crud in the carb and it needs to be removed and cleaned.

I also clean the air filter to make sure there are no issue there either which it sounds like you did.

There is an air/fuel mixture screw that can be adjusted (2 and 1/8 turn out) it is located on the bottom of the carb on the intake side. You usually have to remove the carb to adjust it anyway as there is not much room to work with.

An air leak around the intake can cause some weird stuff as well.

Hope this helps

Swampy