I had a 2000 600 motor and it back fired frequently. Did it stock, did it rejettd and did it with the 660 big bore. Solution: Make sure it idles down (sometimes I had to pull the choke for a second) and let it idle for 20 seconds. Problem solved.

 

I had a 2000 600 motor and it back fired frequently. Did it stock, did it rejettd and did it with the 660 big bore. Solution: Make sure it idles down (sometimes I had to pull the choke for a second) and let it idle for 20 seconds. Problem solved.

:thumbsup:spot on

 

Unburned fuel expands inside the hot muffler and eventually explodes. Letting it cool down before shutting it off may help.

We also had this problem with many lawn and garden mufflers, which would often split open, and the only fix was to add a solenoid to the main jet, and tell people to shut them off at WOT.

 

What would the main jet have to do with it, at idle the sled is on the pilot circuit. Whats the sled doing at idle? Rich or lean?

 

As Jeff G said, you have to let it idle down. Also if your sled takes a long time to idle down to 1700rpm, I would go to 1 size bigger pilot jet, and check your oil pump setting. Carbon will build up with rich oil settings (oil not rich jetting), then you can get carbon/O2 explosions primarily in the silencer or the U section of you pipe. So you will want to check the oil pump setting before changing the pilot, take the slack out of the throttle and then line up the setting. I'm assuming it backfires after driving it under a load for some time and not when you start it in the shop then shut it off before driving it,, as these are 2 completely different situations.
Cheers.

 

Only other thing is to be sure the carb air screws are set 1 turn out and the fuel screws and idle speed is properly set. This will minimize any back firing. Also agree on the idle down. Sometimes flipping the choke to help the idle down issue sooner works also.

 

Lean idle and hot canister. POW!

 

Exactly, it's lean on the idle circuit. This is why a couple seconds pulling the choke lever will cure the problem.

You should hear the e-techs backfire. Sometimes it's delayed for several seconds. You step off the sled, begin walking away and BOOM. First couple times it happens is will scare the crap out of you.

 

Easiest way...you can have a polaris dealer do it...you can buy a tester from a polaris dealer, or if your savvy with electronics build your own. You will need to acquire a 5 vdc power supply source thats well regulated, a digital multi-meter, a #25 tamperproof torx tool and some fine jumper wires to access the tps's wiring harness's 3 connector pins...the ( 5vdc supply), (reference) and (ground) inside the tps connector for starters. The test is performed at wot.

 

Again Thanks! :bc2: