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I'm riding a 00 MXZ 700, it often backfires on me when I start it, and I just noticed the other day that it idles at between 2100 and 2400 RPM unless I hit the choke to bring it down.  The carbs where cleaned lately and the bowl nut is tight.  Are these problems comlimenting one another?  I try to let my machine iddle down before I hit the kill switch, but sometime I can hear what sounds like thunder under the hood when I kill the engine.  I have also got a small crack in the Y of the exhaust pipe right where it comes out of the engine (getting this fixed tonight.  Any advice would be great, the backfire is going to give me a freakin heart attack someday.

thanks,
 

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That crack in the Y might cause the engine to idle higher.  I would wait till that is fixed before you do anything else.  

Dont shut it of untill it idles down to 1700.  If you shut it of above that the engine is still spining fast enough to put more fuel in the engine with no ignition.  This fuel sits in the exhaust pipe and with you go to pull it over next time that fuel ignites giving you the backfire.  

It might just need to be kicked down a notch on the idle which is simple to do.  Get the y-pipe fixed then tell us whats going on.
 

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Thanks Machzzzz1, I think you just answered my question also. I put an mbrp trail silencer on my sled at the beginnig of the year and my sled started to backfire, i thought it was because of that. I also turned the idle up on my sled and it idles at around 2400 rpms. So that's probably it.
 

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What kind of fuel mileage are you getting, and do a compression test.  Mine did the same thing and the pistons and rings were bad at 2300 miles.  I would do the compression test first.   Get the pipe fixed also.
 

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Thanks a bunch guys, I'll get the pipe fixed ASAP.  If that doesn't sure it I'll play with the idle screw.  Had the compression tested and it A1.  I'll let you know how I make out.
 
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