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Polaris Indy 400 1986
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Discussion Starter · #1 ·
Hello, This past winter I bought a snowmobile from a friend. It was an amazing sled and it barely had any running issues other than Cosmetics. It ran great for a few rides but one ride all of a sudden out of nowhere it bogged right now. It would barely move forward for a few moments. Finally, I got it moving again but It wouldn't accelerate at full power anymore, and it wouldn't run right. We couldn't figure out what was wrong with it. We cleaned the Carbs Multiple times, and finally, we replaced the primary clutch seeing as the sled would never get over 6 grand RMP-wise. This seemed to fix the issue for about an hour. It would accelerate full power again. But the second I shut it off and let it sit for about an hour, and went out to ride it did the exact same thing. What do you think my next move should be? I figured that I should clean out the gas tank.
Any help is appreciated!
Thank you.
 

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Did you check for spark or the plugs? On a few 2-cyl sleds I have owned, if a plug fouls, there isn't enough power to drive the sled forward. I would also remove the plug boots from the wires and take off about 1/4" or so of wire to make sure you are getting good contact from the wire to the boot. That will help rule out spark as being the problem.

Cleaning the tank can also help rule out fuel issues, too. It may not cure the problem, but it can't hurt anything, either.
 

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Those were known to have iffy stators as well. And both times when mine went and fyi I used brand new ones from Polaris since I got a big discount, both time they also took out the cdi's. Two different years of the 400s I have owned. I would be checking the stator out as well. The original ones the snowmobiles came with after being that old had just started to corrode and fall apart. Not much I could do about it.

Do what dan said with cutting back the spark plug wires a 1/4" and I would also replace those caps. Get a set of NGK Resistor caps at any auto parts store as they are around 2-4 bucks a pieces. And if you can check out the stator and see what it looks like. Thankfully at least the CDI on those is very common and not all that expensive around 50-70 bucks. The stator however iirc was used on other models from that era. But I can't be 100% sure on that.

Drain the gas from the tank, make sure the fuel line is intact and tygon and that the weighted fuel filter is attached to the end of it. I would be replacing the fuel pump as most likely it is original, along with the fuel lines. Fuel pump you will want a Mikuni DF52-73 which is the updated version of the one it has bolted to the body, I would replace the fuel filter as well. And
 

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Polaris Indy 400 1986
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Discussion Starter · #6 ·
Did you check for spark or the plugs? On a few 2-cyl sleds I have owned, if a plug fouls, there isn't enough power to drive the sled forward. I would also remove the plug boots from the wires and take off about 1/4" or so of wire to make sure you are getting good contact from the wire to the boot. That will help rule out spark as being the problem.

Cleaning the tank can also help rule out fuel issues, too. It may not cure the problem, but it can't hurt anything, either.
I will definitely attempt this when troubleshooting the sled next time. Spark plugs have been replaced.
 

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I don't know if I need a specific number but It seems there is a ton of compression when turning the Primary Clutch by hand

You will need a compression gauge to get this number. You can not tell if you have good equal compression by turning the motor over by hand.
 
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