My 99 ZR600efi has a weak upshift, (not much power shifting up) Where should i start looking at first?
Thanks
Steve in Ct

Sacked out secondary spring,, and/or primary spring. snap

do you still have the stock yellow secondary clutch spring

Yes i do, plus i know it's old. I'll be getting a new spring this week, but i would like to go alittle stiffer.
Steve in Ct

stiffer would slow your upshift even more you want as little tension as you can run to not slip the belt out of the hole that gives you best upshift.

Yeah but when it shifts it loses power, does not pull hard like it should?
Steve in Ct

you need a new secondary spring for sure but I'm not sure how stiff you want it to be, it's pretty much jsut whatever suits your riding style there, I got the stiffest spring they had at Goodwin Performance

The 500- 600 cc Cat sleds only need the yellow or Red/wh sec spring-- don't use big springs like the Green on them,, they won't shift out and you will have crap for Mph. snap

almost all aftermarket kits for the 98/99 zr's use springs stiffer than cat's yellow. bm's purple/white is a bit softer than cat's r/w, goodwin & d&d use springs stiffer than cat's r/w. with a stiffer spring you can use a steeper helix for more pull. cat's yellow is ok for drags but doesn't backshift as well on the trails.

but they wear out quick and you don't get any kind of performance

sorry, i don't know what you're referring to.
i have used goodwin and bm springs that lasted just as long as cat springs. they provide a nice in between if cat's spring rates aren't exactly what you're looking for.