1999 polaris xc 600 hesitating

[EASTCOASTLONGTRACK]

I have a 99 xc 600 that if have been modd'n this year, long tracked it, team tied it , and lot more stuff , i added slp air box ,slp power rack , v force 3 reeds slp boost bottle ,slp twin pipes with canister ,, followed slp jetting specs the problem is if i hold the throttle at the 5500 to 6000 range it is hesitating sounds like ba ba ba ba ba or spurting if i open the throttle more it stops and cleans up and accelerates like hell , same thing when starting from a dead stop with a moderate throttle not more than 1/4 to 3/8 throttle , accelerates up to a certain speed then start hesitating ,not good because 6000 is the rpm's the motor run at will cruise'n down a trail at a steady speed , tried changing needles up and down and turned air screw out 1/2 turns didn't change, pipes seemed to get hot, plug color was cardboard brown ,if anyone got any suggestions help would be appeciated , i am tempted to put the pipes on ebay but i just got done have then coated by swain tech for 300.00 last year i had the boost bottle power pack and stock pipes and it ran fine

 

[BB454]

What you are describing is common on cold twin pipes. Does it clear up after you ride a little? If so then you just need to have some heat in the pipes for it to go way. Singles don't have that problem.
You may have amplified the problem having them coated. They were painted from SLP and their singles are coated. Call SLP and I think they can confirm.

Another thing, those Kehein carb are kind of hard to dial in. Make sure you use the SLP reccomendation for air and idle jets.

 

[Fitz!]

Also when you were reading the plugs did you hit the kill switch when it was sputtering cause that is what you are wanting to read. I personally have had nothing but bad luck with boost bottles on the keihn carbs so you might want to try taking it off and plugging the holes.

 

[FEZ]

the SLP airbox is not easy to tune in the low to mid RPM ranges. Yes, it will make more HP on a Dyno, but every day riding it makes for a blubbery pig IMO.


I would go back to the stock airbox and jet from there with SLP specs. Keep in mind SLP specs are on the very safe side as well.

Use their needle and pilot specs and go down 2 on the mains from what they say with the stock airbox. Also. IMO boost bottles are a bandaid for a poorly jetted Keihin carb. Set up right, they work very well, especially with the power-paks.

Have you replaced the float needles? I would also replace the water trap hoses on the carbs if they are original as they deteriorate from the inside. then replace the float needles and clean the carbs.


The seats for the needles in the Keihins are NOT replaceable and do wear out. This causes a rich condition on the bottom end.