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Motor is getting weak in my 2003 Polaris classic 340 fan. Toying the idea of putting a 550 fan for some extra power. Has anyone ever done this on this model of sled? Is it a fairly straight forward drop in or would it require lots of modifications to make it work? I’m unsure about the mechanical reverse system in my sled working with a 550 with PERC reverse? Would I be able to use the 340 clutching on a 550?
 

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The clutch for the 550 would be the same however most likely the weights and spring would not. You would have to change those out and I would send it out to Indy Specialties to get it balanced and rebuilt as those P-85s are not known for being balanced from the factory. Also what makes you think it is getting weak? Do a compression test hot and cold with the throttle pinned use a zip tie and make sure you CUT IT before starting it up again,lol. As Dan has said he has seen people forget to do that and the sled bolted,lol. If anything I would think about a top end rebuild and doing seals since it is 17 years old.

Now during those years the 550 was not known for being a good engine just a FYI they had piston issues and were blowing up. Polaris knew about it and refused to do a recall instead offering up fix it kits for profit. So think about a rebuild first vs doing all that work.
 

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Yep some of them did but iirc it was the early models that had that P-90, should be easy to find out via Polaris Browse. Also if replacing both springs make sure you replace the secondary buttons people forget those and assume they are fine. Also clean up the helix as well.
 

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The P90 clutch has a different diameter and taper and is used on a lot of the less powerful snowmobiles and on a lot of ATV's. Just make sure what you are getting, as the two are not interchangeable. I had an indy Lite 340 with the P90 primary/secondary and it was noticeably different when side by side
 

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That part number is used on a ton of 340s going back to the mid '90s it looked like. I'd say it was a P-90 and iirc even the driveshaft had a different spline on it for the secondary P-90 as well but someone else would know that better then me.
 

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Discussion Starter #10
So now I’m more leaning towards rebuilding the 340 and playing with the clutching after hearing about the 550s being a ticking time bomb. I’m wanting to get a little more speed out of it so it can comfortably cruise 40mph on groomed trail. As the sled is 40mph is revving a little too high and is probably why it needs a rebuild now. One cylinder is 75 other is 90. Not exactly sure what it should be new but I’d guess 120? Afraid it’s going to pop soon. Anyways I don’t know much about clutching but there is something strange going on with the clutch. It always engages at quite high rpm. Have to hold the throttle and let it rev up high before it engages. It’s done it since new too so I never bothered checking into it. Any idea what could cause this? And secondly how does one go about getting more speed out of clutches? One person here said changing the springs? Heavier or lighter?
 

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Oh yeah you definitely need a rebuild! What is it engaging at? I wouldn't bother with a different spring in a 340 if anything just replace it with a stock oem spring in the primary and secondary and replace the secondary buttons and a new belt. Make sure the belt deflection is correct and that they are square. I'm betting that and the rebuild would really make a difference in it. Really can't do much with those P-90s for clutching. I would rebuild it and go from there. I would also find out why it lost the compression, bad carburetor boots, seals, something had to cause it.
 

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Cheapest thing to try is to give the primary a good cleaning. If the moveable sheave is sticky, the weights have to move at a higher RPM to overcome both the spring pressure AND the sticky bushing before they can start moving the sheave to squeeze the belt. Start by blowing out with an air compressor, then soapy water and a brush, then lots of rinsing. That can't hurt and may help and is cheap. I like cheap! :D

It's a bit more difficult to clean the secondary but blowing it out with compressed air is easy. But usually the secondary does not stick as bad as the primary. As the primary sheaves close, it makes the belt ride up the sheaves and pulls the belt into the secondary. The secondary basically reacts to the primary. Unless buttons are totally worn out or there's huge gouges on the helix ramp, the secondary will work ok even if it's pretty dirty.
 
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