I recently bought a 2002 Polaris Pro X 440 Fan. 2k miles on frame with a fresh rebuild from previous owner. The rebuild was done professionally. I was in change of breaking in the engine, I mixed oil into the gas tank (16 oz/1 pint) to 5 gallons. It ran fine like that until... well until it didnt. It started to bog down and then eventually died and wouldnt start. Took the spark plugs out and I was amazed it was still running, super fouled. Replaced them and rode on. Well now I can hardly take off. The clutch engages at 4500 rpms. The engine cant seem to push past that without me getting off and pushing it. Once I hit 5500 rpms it runs great! I put seafoam in the tank (16oz to 10.5 gallons) and that helped a little. But its still boggy on take off, but will start with me on it (only on flat ground tho, and very slowly) cant even pull its self up a hill from a stop. Newish primary spring so I'm not worried about that. OEM belt,91 ethanol free gas. It ran good for 20-30 miles after I got it. I've put about 180 miles on since i got it and its not clearing up, at least not yet. any advice? I really need the help - 16 year old with his first sled. Broke the bank on it, shes a beauty but I want her to run right

Carb clogged up? I dont know if you have one, but low rpm nozzle being clogged with a chunk of something.

 

thank you so much for this advice! Quite frankly im not sure either. I will look into it!

 

Make sure your main jets are appropriate for the temperature and elevation you are riding. If the jets are too big, the air/fuel ratio may be so rich that it doesn't make any power. And like Lars said, check the pilot jets, as the pilot jet controls air/fuel from idle to about 1/4 throttle... clean as a whistle is your friend!

 

I will have to check that. It was done during the rebuild and the altitude and temp are correct for me, but they could have messed up! My only question is,why would it run fine for 20 miles and then develop this issue? - Thank you for responding

 

those sled are finicky about their jetting, search the site for more info. I have a 340 and it burned down on me once and I ended up jetting up..

 

Hate to say it but check your compression

 

oh i have a bad feeling. will do

 

yep, do what steepndeep said, here are some of the post i read a while ago

Polaris Pro X 440 Fan Bogging?

It's a 2002 Pro X 440 Fan. Seems that when it's warmer than 30 degrees it bogs down on the low end and is fine on the top. Is this because it's a fan cooled and have something to do with the jetting also? Runs like a champ when it's real cold. If you change the plugs it helps out for a second...

www.snowmobileworld.com

 

another string of post

2002 prox 440 fan loading up

Has anyone found the solution to this common problem for the 2002 prox fan? At cold temperatures (below zero) the sled runs great, it can outrun many 500s, but when it gets up to above 10, the sled loads up when you stop and you have to get off and then give it some throttle until it gets going...

www.hardcoresledder.com

 

thank you for both replies. will read

 

It doesn't have oil injection? Your premix is kinda rich.

 

it does, but i was breaking in the engine so i premixed. think im supposed to

 

Like cadillac said.. you are mixing at 40:1, which is a bit rich... with good oil, you can safely go to 50:1 which would be 12.8 oz of oil to 5 gallons of gas... but 40:1 should still run without fouling too much. If you are burning down with 40:1 oil premixed, it's not the oil that's the problem...

 

Even professionals can screw up a rebuild. Do the old check for leaks. Spray something around the base gasket while it is running and see if the idle changes.
My money is on the base gasket slipping out. The walls around the base gasket are very thin and the gasket often slipped in/out and would leak.

Something: Brake Clean, Carb Clean, Starter fluid, etc.

 

ya know, i did think my block looked awfully coated in oil the other day, but i figured i just overfilled the tank. Thank you for this advice! I will look into it and let you know

 

That would seem a bit excessive, unless the oil reservoir is small. Most of the sleds i have had go about 2-3 tanks of gas on one tank of oil...