View Full Version : backfiring problems

12-29-2008, 11:08 PM
i have a 2000 800 RMK with some twin pipes
i tore it down full rebuild new crank, pistons, the works and it has under a 100 miles on it. it backfires at idle and when it decelerates after you rev it ,it's on the pto side of the sled the other cylinder runs fine but the pto side doesn't run at all. i checked spark and it has a consistent spark to it. but the cylinder is way wet and isn't running on it at all. at idle or medium throttle. i put new exhaust gaskets on it and went through the carbs twice. if anyone has any ideas on what could be wrong that would be sweet!! thanks

12-30-2008, 11:34 AM
motorcycles do that when you change pipes. I don't know a ton about it. I like the popping sound on my motorcycle so I didn't fix it. But on the forums I visit they explain a way to get it to stop popping. May work on a snowmobile. You equalize the two cylinders so no cold air is getting sucked in making the loud pop from back firing. Most put a marble in a hose used for emissions and restrict the air from getting in. some put a hose between the two cylinders so they equalize.

Long story short. I don't know if this will help the backfire on your snowmobiles but look for somewhere that cold air is getting into the cylinders. PS I know nothing about backfiring, snowmobiles, or what has been referred to as an "engine" on the colored box I watch my stories on.

01-01-2009, 09:25 PM
thanks for the suggestion! it's been a real fun one to fix thats for sure!

01-12-2009, 11:08 AM
I had the same problem with my Mtn. Max 700. I actually put a half a can of deicing alcahol. Some reason I think there was a little water in the sled which Iced up in the carb lines. The alcahol supposed to get rid of it. I've heard if the sled has sat with a very empty tank condensation will build up in the gas tank letting small amounts of water build up.

01-12-2009, 09:35 PM
i figured it out, there is a sensor in the RMK heads that i thought was just a temp sensor but it actually sends a frequency to the computer that if it's too hot it retards the engine and makes it run like crap. well i looped that sensor so it wouldn't read it and walla! i got a new one and it runs like a champ!

01-13-2009, 08:52 AM
sweet! I love it when you figure out a mechanical problem that has been a pain. Good work.

01-29-2009, 09:27 PM
so actually it only semi fixed the problem
it's backfiring on the idle now, and it's only on the PTO side of the sled