my zr600efi 1998 is a little slow .new clutch wieghts, springs ,bearings, belt, gears are 20 and 39 good compresion i marked cluthes and they areopening and closing to the top and bottom . it has good power but its not going past 70 in light snow. any body have any sugestions p.s wieghts are 48.5 g. clutch is climbing to the top

yep sumthin must be wrong, I was doing 80 yeasterday on my '00 500 M/C efi and Had a '00 600 M/C right on my butt chasing me he had 78 on his speedo and we ran full onion for a mile and a half but this was on loose snow packed road. Was turnin 9.6 on the tach couldnt get anymore out of it. Bout 200 miles on the new topend.

Power valves working properly??

no powervalves in the 98's.

what are your peak rpms?
is your clutch stock?
yellow/white primary spring, yellow secondary?


yep sumthin must be wrong, I was doing 80 yeasterday on my '00 500 M/C efi and Had a '00 600 M/C right on my butt chasing me he had 78 on his speedo and we ran full onion for a mile and a half but this was on loose snow packed road. Was turnin 9.6 on the tach couldnt get anymore out of it. Bout 200 miles on the new topend.
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9.6 as in 9600 rpms?
please tell me that's not true!
if so and your tach is accurate i'm surprized your engine hasn't exploded yet.
you should be at 8500 with stock pipe.

8300 rpm stock springs i might of put driven sping in wrong going to check

I have to bring this one back. Did you get it fixed??
I'm having a very similar problem. I'm pretty sure its in the clutching. Sleds runs perfectly, but doesn't have the grunt or top end it did last year. Feel's like my power valves are not opening up, but its running perfectly, so I'm pretty sure they are ok.

Should you be able to move the driven clutch by hand? Seems like I used to be able to, but now I can't. I was going to start a new thread, but with the software update going on, it won't let me.

Sorry about the power valve comment earlier, I had that problem last year. Didn't think about it not having them.

I have to bring this one back. Did you get it fixed??
I'm having a very similar problem. I'm pretty sure its in the clutching. Sleds runs perfectly, but doesn't have the grunt or top end it did last year. Feel's like my power valves are not opening up, but its running perfectly, so I'm pretty sure they are ok.

Should you be able to move the driven clutch by hand? Seems like I used to be able to, but now I can't. I was going to start a new thread, but with the software update going on, it won't let me.

Sorry about the power valve comment earlier, I had that problem last year. Didn't think about it not having them.[/b]

ya i got it engine stop a little loose spring in wrong hole made a big difference should maybe go to 50 g wieghts as it revs a touch high now 8600 8700 if pinned but might be able to adjust a little more