02 Mountain Max 600 Cutting out at high rpms

Q

Quebecsledder

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Jan 18, 2020
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Western Quebec
Hello all, I need some help as I am at a loss to figure this out

Sled idles and runs fine at low rpms but once it reaches the 6000-7000 rpm stage it powers down. No dash indicator flashes, carb boots look good, plugs nice tan brown .. anyone else experienced this issue??

I have got lots of miles on this sled and it has been nearly trouble free.

thanks
 

Have you ever change your in tank fuel filter? Probably plugging up... When is the last time your carbs were therouly cleaned and settings verified?
Where are your carb needles set at?
TPS by passed?
 
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Never changed fuel filter, carbs are spotless and needles are good. I was wondering about the tps but I figured the dash light would flash or something plus I know next to nothing about it. when I bought it from the dealer I do remember him mentioning something about the tps but that was in 02 and the dealer long gone.
 
You can bypass the Throttle position sensor? Did you mean TORX switch? I didnt really know anymore ever messed with the Throttle position is all that's why I ask. The TPS is on the end of the carb rail on PTO side if you needed to check it.
 
Sorry

I ment the safety throttle switch on the carb rack.

Don't know if it's at the same place for a 2002 as it is on my 2000...
 

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The tors switch might do it but usually if that was starting to mess up it would happen down low. I dont think it would let you get over 4000 rpms. I know on my brothers he was having the issue with his SXR had trouble finding it but it was a broken wire on the coil harness
 
Spark plug caps isn't a bad idea, cheap and easy to replace. I've also seen plugs do this that are starting to foul out, they are fine at lower rpm but don't perform at WOT. Used to have that happen all the time on two stroke dirt bikes.
I would do new plugs and caps to start.
Also, when's the last time you went through the clutches to clean and look for worn components?
 
Thanks for all the tips... fuel filter was fine and there are fresh platinum plugs, wires and caps, although cheap caps and wires, not Yamaha parts. I have began to think it could be a coil issue, my 2 stroke outboard one time acted similar to this and it turned out to be an ignition coil. Will also begin to chase down the other leads, nothing worse than electrical problems!
 
What brand and kind of platinum plugs? I've seen different plugs do some strange things. IMO there is nothing better than stock NGK's for a Yammie.
 
interesting observation about those high $platinum plugs, never used them b 4 till now, always ngk or champion. what ever one was on the rack got bought. the problem was present b 4 the plugs were installed.
 
Ok, re-read this thread. You say it "powers down", I assume you don't mean it shuts off, it just hits 7k rpm and gets a bog and won't pull any higher rpm's.
This now makes me think of the little "top hat" filters in the carbs where the needles are. I assume a MM has these, this is the next thing I'd check. Many have found these screens all plugged up and greatly restricting fuel delivery.
 
A quick run down on what was done and the outcome.. The TPS was bypassed to eliminate that potential problem only to encounter another - Stator was shot. Two junk China aftermarket and then a Yamaha stator and it is running like new. While it was down had the original slide,idlers replaced and jack shaft bearing, after all it is an 02 - where I live there is little sand, no salt on our roads and not shortage of snow normally. Went to the cabin and back yesterday, maybe 50km round trip and I was one happy camper. Now I need to replace the track come spring (original) and would like to replace it with the same style - 2 inch paddle. If I could I would buy Yamaha replacement but I hear they are not available - any suggestions??
Thanks for all the help. Keep the rubber side down!
 
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