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Discussion Starter · #1 ·
i think the reason why my sled isn't going over 40mph is because my valves are not opening, i fully disasembled my valves and cleaned all the components in varsol...on the end of the ves cap there is a hole, i tried putting a awl in the whole and reving the engine while it was jacked up off the ground to see if the valve would open, if the valve would open the awl would be pushed out a bit but nothing happened when i tried that, so i took off the ves again and used a air gun through the small chambers to see if the valve would open in my hand and sure enough it did...is this the proper way to see if the valves are working when i rev my XC, any other posibilities why my valves arn't opening??

Thanks
 

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You need to run over 7000 rpm's to open valves. Are the bellows torn or leaking.
 

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There is a very small hole in the jug that gets plugged sometimes and can cause the VES not to operate correctly. You can feed a piece of mechanics wire through it to make sure it is clear.
 

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Discussion Starter · #4 ·
my sled only revs up to 6500 rpm then stops like a if there is a governor on it, the jug and piston on the PTO side is brand new, could the holes on the exaust side jug be blocking the air and stopping it from reving up
 

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I have never experienced that senario but I guess it is possible. Take the VES back off and look for the hole and check for it to be free, at least it will eliminate it if it is free.
The limiting of RPMs, is it all the time even if your track is off the ground?
 

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I don't mean to insult your intelligence or anything, but are you sure both cylinders are firing? I know it sounds like a stupid question, but in the past I have started trying to troubleshoot a problem where the engine wouldn't reach operating rpm and thought for sure it was running on both cylinders, but it wasn't.
 

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Have you checked to see if the clutch is binding or components on it are???? I feel it is something more than the ves system???
 

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Discussion Starter · #9 ·
yes i have checked the clutches and they are not binding...i'm thinking that it is electrical now, that i have checked all of the mechanical components...i have an idea of what it may be, on the side of my carb there is a elec harnes going to one of them, is this harness that releys to the CDI to initiate the proper speed of spark as ur engine revs up, ex. as u increase the trotle and open up the carbs, the spark speed increases....does anybody have a service manual that they could scan for me or a web link which has one online, it would be GREATLY appreciated
 

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Might be off topic for what the thread has turned to, but for the original question. A good way to see if the bellows are torn is to push the valve up and put your finger over the hole on the outside of the valve housing and let go of the actual valve. If it stays where it is the bellows are good. If it goes back to original due to the spring pressure the bellows are no good.
 

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Hey I know you say that you already checked your clutches over, but just make sure you checked the bushings over. My cousins 500xc buchings were worn right flat, and he had the exact say problem as you with the RPM's
 

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Discussion Starter · #12 ·
i have carried this thread into another one called CDI problems now, i have disassembled the primary clutch and the rollers are fine, i think i may have narrowed it down to an electrical problem, CDI may have a short, stator on the fritz or throttle position sensor could be going or re-adjusting....its hard to find out because what ever went wrong, happened over the summer when it was sitting
 

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I believe the temperature sensor/switch mounted in the center of the heads has 2 wires on the 02. We have had a lot of these go bad and limit the RPM's to protect them IF THE SLED OVERHEATS. When they go bad they simulate the overheating condition and retard the spark.

If it is disconnected (or the wiring broken or shorted) it does the same thing.
 
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