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Discussion Starter #1
We have a late 80's Polaris indy Trail and when it is warm it doesn't have any power at low reves.  If you get it up to speed it picks up and goes.  I say if because you need to be going down hill on packed snow to get there.  I took of the carbs and cleaned them but they looked fine, no gunk any where.  

any idea what could be causeing this?

One of my dad's friends said that it could be the crank seals and to spray starting ether or somthing flamable by them while the engine is running and see if it changes rpm..
 

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Have you ever put new clutch springs in it? Your clutches may be sticking so that you are basically trying to start out in "third gear".

Lee
 

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Be VERY careful spraying either into your airbox/carbs.  Plus, lets say the seals in the crank are bad so your not getting enough "suck" from the bottom end to get the needed fuel in.  If you spray either into the airbox i'll bet my job that the R's will pick up no matter what the issue is.  Like stated above the clutch is a fairly easy place to start.  Run the sled on a jack and work the brake and throttle to see if the secondary is back-shifting correctly. hth  eric
 

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Start the motor
spray wd-40 (which is just ether and penetrating oil)
down around the outside, I'll say it again outside (not in the airbox) of the lower part of the motor. Do this on both sides.
If the RPM picks up crank seals are shot
 

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It could be a few things. How long have you had the machine? Did it ever run good? Check compression. It could  be jetting. Too rich of main jets will cause problems like this. It could be clutching related. Have the clutches ever been cleaned and springs replaced? When was the last time the belt was changed? These are all things that should be looked at.
 

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Assuming you have had this machine for awhile and it didn't used to do this under these same conditions, I'd say the problem is more likely in the drive train than in the carbs though it might also be be the engine. The easiest problem to find correct is the belt. Make sure it is within specs. I would look at the primary clutch next especially if you have not done regular maintenance (inspection and lubrication). The outer bushing (on the outside plate) will often wear out before it is noticed and can ruin the shaft it slides on. Corrosion on the shaft can increase the likelyhood of that happening. The weights on a machine that old did not have bushings and could easily be so worn that the weights don't swing in and arc perpendicular to the shafts they are mounted on. If the clutch has not been kept lubricated the weight rollers may be stuck, no longer round, etc which will obviously cause serious power loss. Compress the clutch with a bar or clamp (remove the belt first) to inspect the weights, rollers, etc. These are the most common and easily determined problems in the primary. The secondary could also be the problem and I think you will most likely find problems in that one to start with the sleeve bushing that rides on the part of the helix you see behind the mounted clutch.  You should see light wear marks on the exposed portion of the helix but no serious scratching. If there are scratches or gouges in the helix it will need to be replaced along with the bushing. It could also be the slider buttons found internally though they rarely wear out.

The engine problem alluded to by a couple other posts would, I think, more likely cause starting trouble and/or fuel starvation at higher speeds due to fuel pumping problems. (That is the way to check it: spraying WD-40 or starting fluid by the seals.) Lack of decent compression (too much ring and/or cylinder wear) would more likely cause a lack of low rpm engine power.
 

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Hello,
I had the same problem and it took me about 6 months to figure out. I had the same symptoms, and I tried everything else that was above mentioned, but if you want to save yourself time and money do this!
1)The problem is the choke plungers. The seal is bad
2)Take two round pencils with full erasers and unscrew the choke at the carb
3)Stick the pencils eraser down deep into the choke hole until it hits bottom and provides a snug seal
4)Pull pencils out and start engine.
5)Wait a minute and then repeat step #3.
6) This mimicks the choke plunger working.
7) Close shroud and drive snowmobile at length with pencils in the Chokes.
8)This should tell you that it is the plungers if it works better
9)Go to local dealer and buy new plungers and install them

This should work for you!
Tell me if it Works!
Dustin
 

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Dustin,

That would be a big "Duh". You're quite right about that possibility and diagnosis. Funny how one doesn't think the same when they're in front of a keyboard rather than the machine. That should have been one of the first suggestions as well, "the chokes"!!
 

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Discussion Starter #10
Ok this is what we have tryed so far. with no luck
Spraying stuff by the crank seals: (did nothing)

compression: (really good around 120ish)

belt : it's new and the most it has ever been sucked it the driven pully is a 1/16.

Cleaning cabs:  nothing yet.  We didn't have a rebuild kit but every thing looked ok

I guess next we will try the choke stuff..  We have had the sled for about 3 or 4 years and it started last year..

Eric
 
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