1999 SXR 600 won’t rev past 7000

88 yamaha 570

88 yamaha 570

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Joined
Jan 3, 2010
Messages
343
Age
33
Location
Bridgeport, NY
Hey guys, been a while since I’ve been on here but i got a customer who was given a 1999 SXR 600 that supposedly needed the carbs cleaned, i gave the sled a once over and pulled the carbs apart to clean them but they were in good shape, sled would have a massive backfire when throttle is punched from a stop and would rev to 6K then slowly move up tawardw 7K and fluctuate, i decided to flush the tank and put fresh fuel in it and did some electrical testing, I’ll post a picture of my findings but my question is do you guys think this issue could be caused by the source coil being out of spec by about 40% before i sell him any parts he doesn’t need? Only other thing i could think of would be needle clip positions as i didn’t touch any of that. Could needle clip position cause a top end powr loss like this?

IMG_2597.JPG


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To me it sounds like a bad plug cap or reed with the possibility of a bad donut gasket contributing too.
 
Reed gaps were less than 1/8” so i don’t think that’s it, one exhaust gasket was bad and leaking the other seems fine. Haven’t tried swapping plug caps but I’ll try swapping the coils off this other sled and see what it does.


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If you have gaps in the reed petals, that would the the first thing to remedy, before you go through the work of a stator change.
Reed petals have a slight curve to them, and must be installed so the petals are tight at the end.
Should be resting against the cage at the tip.
 
Stator fixed the problem guys. Like i said it tested at less than half of standard spec so i wanted to replace that. The reeds will be forced to seal up fully with backpressure anyways so the minimum gap i have hasn’t effected it yet. Hydrov24, if you want PM me I’ll help you through testing yours to make see if it’s stator related
 
Thanks for posting the specs for the stator. The stator on this sled checks out all within specs. This is a friends sled and it just runs "flat". Backfires lightly through the exhaust and has no power. Checked the wiring harness under the motor and it was fine. Carbs have been completely gone through and are clean. Maybe a weak primary coil, but I have no way of checking. Any other thoughts you might have would be appreciated.

Have you ever seen rub through on wires in the dash? Just noticed that the tach is not working also....

I don't have enough posts to private message;)!
 
HydroV24 said:
Thanks for posting the specs for the stator. The stator on this sled checks out all within specs. This is a friends sled and it just runs "flat". Backfires lightly through the exhaust and has no power. Checked the wiring harness under the motor and it was fine. Carbs have been completely gone through and are clean. Maybe a weak primary coil, but I have no way of checking. Any other thoughts you might have would be appreciated.

Have you ever seen rub through on wires in the dash? Just noticed that the tach is not working also....

I don't have enough posts to private message;)!
Click to expand...

What’s the info on the sled? If the tach doesn’t work i would start there. That way we can find out what RPM it’s acting up at
 
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