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We have a 2000 600 xc that backfires after you start it up,sometimes pretty major. Normally only will do it once,maybe a few small pops, but warms up and seems fine. Just cleaned carbs today,did not see anything out of the ordinary,compression good,could it just be the older gas. Also is somewhat of a bear to start,chokes are adjusted properly.Any ideas.
 

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heres a copy of my post labeled 'cold blooded 01' I had the same problem.

Cold Blooded '01's

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I have a 2001 XCSP 600 that was as cold blooded as heck. It has the Mikuni TM38 carbs on it. I did some playing and research on my own along with advice from you guys and found a happy solution. It isn't perfect yet but is 95% better. I always had to babysit the sled to warm it up. Now I don't and I have started it in single digit temps. All you need to do is up the Idle/Starter Jet one size(mine was 140 and now is 150). The Polaris dealer that I ordered it from told me there's no way it will work and that I needed Pilot jets. I told him to just think about it. The Idle jet controlls fuel flow at 0-1/8 throttle. if its cold blooded, you need more fuel. Now I just have to tune my mixture screws a little bit until its perfect! I hope this helps someone else with the same frustration!
 

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We have a 2000 600 xc that backfires after you start it up,sometimes pretty major. Normally only will do it once,maybe a few small pops, but warms up and seems fine. Just cleaned carbs today,did not see anything out of the ordinary,compression good,could it just be the older gas. Also is somewhat of a bear to start,chokes are adjusted properly.Any ideas.
Most likely a "lean pop". You could possibly richen the idle mixture or you could just let the bugger warm up good. My 01 has this problem and I know that changing the pilot air jets to a larger size would "fix" it. I choose to let it warm up good before I ride it.

I use the condition as insurance against cold seizure.
 

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heres a copy of my post labeled 'cold blooded 01' I had the same problem.

Cold Blooded '01's

--------------------------------------------------------------------------------

I have a 2001 XCSP 600 that was as cold blooded as heck. It has the Mikuni TM38 carbs on it. I did some playing and research on my own along with advice from you guys and found a happy solution. It isn't perfect yet but is 95% better. I always had to babysit the sled to warm it up. Now I don't and I have started it in single digit temps. All you need to do is up the Idle/Starter Jet one size(mine was 140 and now is 150). The Polaris dealer that I ordered it from told me there's no way it will work and that I needed Pilot jets. I told him to just think about it. The Idle jet controlls fuel flow at 0-1/8 throttle. if its cold blooded, you need more fuel. Now I just have to tune my mixture screws a little bit until its perfect! I hope this helps someone else with the same frustration!

Idle jet? The TMs have a pilot jet, main jet, needle jet, air jet, and starter jet. There is no idle/starter jet. The ONLY time the starter jet is in operation is when the "choke" is engaged. With the "choke" off, a plunger seals off the starting circuit.

There really is no choke per se. There is a starting circuit that opens fuel to the starting jet which richens the mixture.

The only thing you could call an idle jet on a TM carb is the pilot.

@ hardcoresledder.com it is often referred to as PAJ.
 
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