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Discussion Starter #1
New to this forum, but I have a question regarding a recuring problem on my '95 Polaris XCR 600. Late last year my buddy was riding it, and from what he's told me it just stalled out (like it was flooded) at low speed. We couldn't get it started right away, so we let it sit for a while. We finally got it started, but it ran on 2 cyclinders (the machine is a triple), until the third one kicked in. But it dropped out (off an on), and evertime it kicked back in the engine knocked (I assumed that it was the third cyclinder lighting off the excess gas). I thought I had a plug problem, so I changed the plugs, and checked out the wiring to make sure that I had a proper spark in all three cylinders. Everything was ok. Just last weekend (next riding season), same buddy and I went for a ride, and the machine stalled out again (when I was getting off to check out something on the trail), and would not start. It was flooded, so we waited and eventually got it started, but not before towing it and letting it sit for 20 odd minutes. The machine runs great at high speed, and all the trouble I've been having has been during low speed runs. Things that I've been told to check: clean the carbs, change plugs, check wires, look at water pump. Anybody have any similar experiences? or recommendations/advice?
 

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i have the same sled and had that same problem but not as bad. i had all new chokes put on and did everything that you mentioned and i havent had a problem. also what type of fuel are you running in it. reg, premium or mid. ? that would explain the knocking if you are running the wronge grade of fuel.
 

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Discussion Starter #3
The gas that I have in the tank is low grade, but it is above the 87 octane minimum (but not by much). Since I last posted, I checked the jets that are installed and noticed that I might have been running very hot as the outside temp was around +5C and the set of main jets that I have installed should have a minimum operating temp of approx -12C. Nevertheless, I do plan on fiddling with it tomorrow, and we'll see what we get. I started it tonight with no problem.
 

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check the compression on your cylinders and see if they are all the same. they should all be within 5 - 10 pounds of each other. ya might have leaned out a cylinder from a bad crank seal and stuck a ring.
something else to check, is the wires.
I had a wire rub against the steering post and wore the coating off. everytime I hit a mogul ( or bump ) it would catch and ground out then shut the machine down.
one of those arse biters. :eek:
 

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I think it works the other way... if you are running in a warmer temperature than the jets are for you are running the sled rich... and if the temperature is lower than the jets are for you start to lean it out and run hot.
 

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Discussion Starter #6
Does that mean that the jets that I was running would make the fuel mixture rich? If that's the case then that would explain why the machine flooded so easily?!
 

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I have the same problem. One thing on the jets.....smaller jets are needed at warmer temperatures as the air is less dense. Smaller jets are also needed at higher elevations because the air is thinner or less dense. Race cars run best at sea level elevation and add that with cooler temperatures and it can't be beat. Running lean in a snowmobile is very very bad. Burns up the engine. My sled, a 95 600 XCR, starts with a very easy 1/3 pull of the cord and idles fine and takes off great. Problem is when it has been ridden for 15-20 minutes and then is shut off and upon restarting a couple of minutes later it starts easy but when you hit the throttle, it bogs and will NOT rev up, it just goes "BOAWAH!" You have to feather the throttle ever so carefully to get it up and then once it hits 1500 rpm ( from 500 when it bogs) it is just fine. The other thing it does is when you ome to a stop after the same 15 minute ride it idles at 4,000 rpm. If you choke it for a split second, it drops the RPM down to 1500 and it will idles just fine right there. If you bring the RPM up to 3,000-3,500 RPM after it has been brought down to 1500 RPM it will hang up at 4,000 RPM again. If you choke it it will drop to 1500. I have 290 main jets (300 on PTO side), size 30 pilot jets and Q2 nozzles with the clip on the middle notch. Riding between 4,000 - 7,000'. The sled has PSI pipes. The carbs have been synchronized, they open equally at the start and all open wide open an equal amount. Note, the sled had P8 nozzles with 260 main jets before and had the same problem. I have been told several things including the crank needing reindexing, the lower seal leaking, carbs needing synchronizing, carbs dirty, running to lean, float bowls adjustment off, vent hoses not the same length, pipes making it too lean, not enough heat being retained in the pipes-ceramic coating needed. Keep working on it. If I find something that works I will post it here for you. I know that a lot of guys have this very same problem. Somehow I think it is one thing that is causing this same problem.....
 

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Discussion Starter #8
Thanks for the input! Now that you mention it, it is the 15-20 minute ride that keeps kicking my *ss. I'm going to take it out again tomorrow and see if I can ride it for a while.
 

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600xcrrider, I know for dirtbikes that if it has the same symptons you just mentioned, its can usually be a bad ignition side crank seal. For dirtbikes, the left side crank seal goes out to the ignition stuff. So after you've run the engine for a while, the area inside the ignition area becomes hot from the engine heat, then this hot air gets into the bottom end where all the fuel and air mixture is, combining with it and leaning it out some. But I'm not sure if the snowmobile engine is that similiar to dirtbike ones. What I would try doing first, after the 15minutes when its acting up, is adjusting the air screw on the carbs which would impact the mixture during low rpm. Try richening the mixture by allowing less air in. Just a thought. Maybe you already tried this though. good luck
 

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Glitch, I had not tried the adjustment of the air screws. Turning the screws clockwise, is that the adjustment for a richer mixture? I started it this afternoon in the garage in 22 degree air temperature and it did the same thing as I described earlier. It will start out at 1,500 rpm and then if you increase the throttle to 3,500-4,000 rpm and then let off the throttle it will come down somewhat to about 3,000 rpm and then stay there. If you choke it for a split second it will drop down to 1,500 rpm. Pilot jet? I have the sled set up to the specs that PSI recommended.

Thanks :)
 
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