Help, my 98 Indy RMK 600 is spitting ignited gas into the air box and exaust... HELPP

[Simonsledd]

I bought a beautiful 1998 Polaris Indy rmk 600 last year knowing it was gonna need some work, the previous owner told me he had trouble with it starting, he said it had a misfired and shot lit gas into the air box which melted a lot of stuff. The first thing I did was take the carbs out, clean them and put new gaskets in them, then I replace all the melted electrical and fuel lines. I took the fuel pump apart which looked in bad shape, cleaned it out and put it back together. I'm not sure if the fuel pump is really working and/ or if its part of the problem. After 1 week the sled was clean and put together I went for the start up. The sled started right away without problem, it seemed to idle well and it sounded amazing in high rpms, so I let it idle longer, but then within 5 minutes or less it had a backfire. The backfire had pushed the ignited gas from within the engine out and through the carburetor and I think the exaust, creating a fire inside my airbox, and on the garage floor. The fire melted all the same electrical and fuel lines that I replaced and it seems to have pooched my fuel pump. So now that it has cuaght fire twice, I'm not sure what I should be looking into next. It there anyone out there who might know what's going on here, I talked to a mechanic about it and he became more confused about it then I was. Really don't want to let this sled go. Thanks for all you're help.

 

[Caper11]

Whats the reeds look like?

 

[Simonsledd]

Whats the reeds look like?

When itook the carbs off there was a small amount of build up on the egde of the Reed's, but honestly they look quite pristine

 

[mountianguy]

Most times when there is ignited fuel in the intake you have a timing issue. I would start checking the electrical system related to timing, make sure all the part numbers are right for that year. Pull the mag apart check the rotor, stator, timing sensor make sure its the correct key. Make sure the timing is right. Check the Cdi and all the wiring make sure its not shorted or grounded some where. Just thinking what else may cause this, check your exhaust make sure its not plugged a partial blockage may let it start.Bit of a long shot but its free.

 

[Simonsledd]

Most times when there is ignited fuel in the intake you have a timing issue. I would start checking the electrical system related to timing, make sure all the part numbers are right for that year. Pull the mag apart check the rotor, stator, timing sensor make sure its the correct key. Make sure the timing is right. Check the Cdi and all the wiring make sure its not shorted or grounded some where. Just thinking what else may cause this, check your exhaust make sure its not plugged a partial blockage may let it start.Bit of a long shot but its free.

When I purchased the sled I had to replace the main wiring harness, and one of the connections that went into the engine was melted badly, so I had to improvise by splicing the wires. I remember looking at how the wires were put in the connection and thinking that it looked a bit off, but I didn't know exactly how. Electrical is definitely not my strong suit, so I just put the wires back in the way I pulled them out. I might have to cautch up on my electrical skills if I wanna get her fixed.

Does anyone have any suggestions of where I can buy old Polaris snowmobile parts? Sounds like I'mma need some shortly.