my sj hit rev limit so early

hello all, after my atp flame total loss went to heaven, I decided to install stock electronic and today after it is done I tested my ski and it revs fast then hit the rev limit. I tried to change prop and another stock cdi, coul, etc still hit so soon. my mods are 62t cylinder with 85 mm pistons, ada head, factory pipe type4, dual 46 mm buckshots with carbon reeds.
what causes the rev limiter to hit so early and how to fix?
thanks in advance
 
I would first make sure youre pump is functioning correctly. Are you running a tach? I would want to see what my rpm's are doing. You could also look at modifying your stock cdi. https://www.x-h2o.com/threads/superjet-cdi-modification.496/
hi I checked my pump and it is good but my prop is 14/17 solas which people said it is too small so I also tried another prop and still the same. So I guess I would have to change to adjustable cdi?
 
If it's hitting the Rev limiter way early, the cdi is going out. It's a diode that controls the limit. There's a thread on here somewhere on how to hack it open and solder across to delete that diode.
Hmmm my ski is all of a sudden doing this. I was told stator but this would be good news. Rather it be cdi. Going to switch one out and see thanks
 
If it's hitting the Rev limiter way early, the cdi is going out. It's a diode that controls the limit. There's a thread on here somewhere on how to hack it open and solder across to delete that diode.
hi the cdi is new. I switch the cdi with my friend's ski (I used his and he used mine).
We also switch the coil with same result. his ski is stock except b pipe and not hitting the rev limit early like mine.
 
61x system will work the same as 62t. 61x stator in a 62t flywheel won't run right at all. Many years ago a local had that problem. If you swapped out the cdi with a known good one, it's not a cdi or Rev limiter problem
 
My kids SN is doing this after 62t/61x swap and factory pipe and RN waterbox install, slight compression bump with new head. Thinking its MSD enhancer time.
 

Myself

manic mechanic
Location
Twin Lakes AR
I've seen this a couple times through the years on yamaha twins. A faulty voltage regulator can cause a rev limiting situation at around half throttle. Check the voltage on the battery at idle and watch it as you rev the engine.......what does it do when the rev limiting starts?
 
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