Xc Sp 700 Backfiring Problems

[Logan_Martin27]

Hey Guys,

My 99 Polaris Xc Sp 700 has a backfiring problem. I have cleaned the carbs and I have also replaced the reeds because they were bad and I read that bad reeds could contributed to a backfiring problem. The new reeds helped a little but it still backfires when idling and at take off. What could it be?

Thanks

 

[minus40]

If it's popping in the carbs it's lean. Up the pilot or adjust the fuel screw. Keihin carbs are notorious for this. I used to adjust damn near daily. A neat trick was to use a welding rod, clean off the flux and hammer a flat end in it for a long screwdriver and store in the hood foam

 

[omernikski]

Does it backfire after its at operating temp?

 

[Logan_Martin27]

It is actually running a little rich to be honest.
And it still backfires at idle even after riding for a while.

 

[omernikski]

Did you make sure you could see light through your pilot jets? Sounds like you may have partially plugged jets

 

[Logan_Martin27]

Yes I did. I cleaned my main and pilot jets very well. Do you think if my fuel/air mixture is off, if that could potentially be the problem?

 

[omernikski]

I just completely rebuilt the kehins on my 98. I think the fuel air screw is set at 1.5 turns. I'll verify it today. I also had backfiring at an idle till I syphoned out the old fuel and put fresh gas in

 

[Logan_Martin27]

I just set the fuel/air screw to 1.5 turns today and that helped a lot. I have an exhaust leak so when I fix that, hopefully tomorrow, the backfiring should stop. Thanks for your feedback.

 

[omernikski]

Right on. Yeah the screws are at 1.5 turns. Once the temp drops more it should act better

 

[Logan_Martin27]

Thanks for the help. ��

 

[Logan_Martin27]

Hey guys,

I am still having the same problem with my sled, I can't figure it out. I fixed the exhaust leak and I have done everything I can think of and it still backfires. Can anyone think of something.

Thanks

 

[retiredpop]

Have you set the float level? It's a little different procedure than the Mikuni. See attached.
You have the PWK 39mm.

http://www.carbparts.com/keihin/needles_tuning/jetting_your_carb.htm

 

[TRS]

Did you check the carb flanges for cracks.

 

[polaris bob]

Best guess is either a air leak as mentioned above or the ignition system is getting weak.

 

[retiredpop]

Turn the idle mixture screws in until it idles without backfiring and has good throttle response. Turning them in richens the mixture as they are air screws. I believe we ran ours about 1 turn. If you get to less than 1/2 turn then you need bigger pilot jets.