XC500 SP won't hit peak rpm's about 50% of the time

Hey everyone, anyone have any suggestions that I can do to fix this on my own? Here's the sled and what's happening:

2002 XC 500 SP with power valves
1,900 miles


Sled starts, idles, and runs just fine 50% of the time. Peak speed is normal and peak rpm's are around 8100 rpms. Top speed is normal about 85-90 mph.

However, 50% of the time, sled runs fine until about 50mph but then won't increase past 50mph or hit peak rpms. I hold the flipper wide open, sled takes off normally until about 50mph and then sort of bogs and won't increase in speed. I thought it was the power valves not opening properly, but after cleaning them the sled still has this problem about 50% of the time. If I release the flipper and wait a few seconds, sled will pull all the way to 8100 and run normally. Then, on the next straight away, it will bog at 50mph again. Then on next straightaway, it will pull just fine to 8100 rpms and 90mph

12 months ago, I put the correct amount of stabil in a full tank of gas and ran the sled around the trails for about 30 minutes to get the stabil through the lines. Since then, the sled has been in storage with that same stabil and fuel. I have ran this old fuel out of the system and filled up with a new tank of fuel about 20 miles ago. Could there be something getting clogged in the carbs about half the time? Intake getting clogged? Belt seems to be sitting fine. Clutch issue? Any other thoughts?
 
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This is from another post about cleaning power valves....maybe I didn't clean these ports when I cleaned the power valves?

"As stated above, clean the. also it is very important to make sure the pressure port from the cylinder to the the bellows is not plugged, which very likely it is with not having been touched in the miles that you state. I use a fine drill & turn it by hand, if you do this, be extra careful not to brake it off. The ports do carbon up. "
 

scott_d

New member
I would look at your clutches. stickey weights, bad bushings,secondary buttons, belt or belt deflection.
 

xcr440

Well-known member
As Scott says. I rebuilt the clutches on my 99 XC 500 this past year, night and day difference.
 
Thanks all. Right now, I'm going to start with the clutches. I need to buy the primary clutch puller.

Is it a fuji or liberty motor in the 2002 500 xc sp ?
 

xcr440

Well-known member
Liberty

And when you do start working on the clutches, even the puller, I'd find someone who has the right tools and/or know how. You shouldn't need to do a complete rebuild with only 1900 miles.
 
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Northstar

Member
Sounds a lot like what I had with the wife's '03 600. Launched fine up to 50-60mph or so and up to 7500rpm, then it would creep down in rpm and speed. Would launch again fine from a stop but could not sustain speed or rpm. Took the power valves apart and found a small cut in one of the bellows, so it must be able to open it up but then lose the pressure. Could have been like that for for a while had I not taken it down the road because I doubt she would have noticed.
 
I've got the carbs and both clutches with me now. Going to clean out the carbs first.

Do I need a clutch compressor to proceed with the secondary? What am I looking for in the clutches?
 
Carbs look clean as a whistle inside. All jets are clear and the needles look clear. I can see right through them. No junk or varnish in there........
 

indy_500

Well-known member
Sounds like the primary. No need for a clutch compressor for the secondary, if you take the secondary apart replace the buttons, they're cheap. But I think your problem is the primary... Put a sharpie line on the primary and see how high the belt gets. I don't think its shifting out and is binding.
 

fastmod62

Member
Sounds like the primary. No need for a clutch compressor for the secondary, if you take the secondary apart replace the buttons, they're cheap. But I think your problem is the primary... Put a sharpie line on the primary and see how high the belt gets. I don't think its shifting out and is binding.

I'm thinking the same thing.
 
Clutch 500xc sp.jpg

Thanks everyone. I think you are right....

As long as I have the drive clutch apart, what should I replace (including the part you are talking about) from a standard maintenance perspective? Can't hurt to replace the spring, right? What else as long as I'm in there? Can you tell me what item #s from the attached pic? Thanks
 

indy_500

Well-known member
From a maintenance perspective, I replace cover bushing (#3), weight bushings(not on parts diagram, polaris doesn't sell them seperatly, EPI sells 3 of them for $15), and spring (#5) almost yearly along with cleaning it very well and taking fine grit emery cloth to the clutch sheaves and wiping it down with acetone. You don't have to be too mechanically inclined to take the clutch off with a puller, take the cover off, and do these things. Anything beyond this cost some $ for the tools, or $ to take it somewhere. Not sure how much you know about clutches, but you really don't have to be a genius to diagnose a bad bushing or roller, etc. You will feel it in your hands when you have it somewhat apart or see it even if you have no clue what to look for... The parts more likely to bind that you may need to replace that require special tools include your pucks (#6), rollers (7&8 I think pic is hard to see), and #13 (bushing).
 
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Great info...thanks...here's what I see after taking apart the primary:

# 8 (the rollers) roll just fine. They are nice and smooth and when I flick them with my finger they all keep spinning for a while. Sound OK?

# 11 (1321685 WT/BUSH.ASM,10-54) are all smooth and don't have much wear. However, how easily should these things "swing out"? I can swing them all by hand fairly easily, but get this: when I hold the clutch over my head, only 1 of them freely swings down with gravity. The other two stay put. If I flick them, they move easily, but they don't just "fall" with the gravity when I hold the clutch upside down. Is that significant enough to be causing my problem?

Any other things I should check?
 
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superski

Member
Had the same issue on mine and it turned out to be a bad spark plug cap. I cleaned the clutches, VES & ports, and then the carbs with no luck. I talked to a buddy and he suggested checking the spark plug wire caps - seems they have a resistor molded into them that can fail or give an intermitment spark. You can check them by unscrewing them from the wire and checking with a VOM -they should check at 5000 ohlms +/- 10%. If you tap on them with a screw driver handle and they are bad you'll sometimes see a vairation in reading also. When I checked mine one was good the other read only 480 ohlms. I replaced both caps and put new wire on and it ran like new
 

bigred_tr

New member
The Net !

I did my "P85" clutch this past fall. Look it up on the net..It be your best friend..google... There are a cple of vidieos that you can watch and understand what to look for when you rebuild a clutch.

www.youtube.com/watch?v=k0khXyugGSE


Eaiser than try'n to go thru all on it here

If you start to take a part the spider...need a clutch holder and a spider wrench with a long breaker bar.

But don't know if this is your issue or not but good to check.

P.S. 1900miles?? was it ever rode? I have a 1999 500 XC 13,000miles been riding it ever sice I snow checked it :)

BR
 
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indy_500

Well-known member
Had the same issue on mine and it turned out to be a bad spark plug cap. I cleaned the clutches, VES & ports, and then the carbs with no luck. I talked to a buddy and he suggested checking the spark plug wire caps - seems they have a resistor molded into them that can fail or give an intermitment spark. You can check them by unscrewing them from the wire and checking with a VOM -they should check at 5000 ohlms +/- 10%. If you tap on them with a screw driver handle and they are bad you'll sometimes see a vairation in reading also. When I checked mine one was good the other read only 480 ohlms. I replaced both caps and put new wire on and it ran like new
Your "buddy" is xcr1250 aint it? I'm doubting it's the plug cap because this happens to the O.P. 50% of the time, if it was the plug cap it'd probably happen every time.
 
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