GPZ550/615 frame off restoration clutch slipping after power up

Sir's ET: All

I rebuilt the engine with the 615 kit, put a 4 into 1 Kerker on and ported/polished the head, it seems to be making some decent power now and the clutch is slipping right at about 6000rpm as the power comes on.  Anybody run into this before?   Does anybody make racing clutch plates or heavy duty for the GPZ/KZ550 form factor?  

Thanks
577Nitro-

How old are the clutch springs?

EBC sell replacements that are 10% stronger than stock and much cheaper. You can also run shim washers on them to gain a little more stiffness if its needed. They do back off over time.

OEM Kawi fiber plates are the best, but if you need aftermarket look to Barnett.



Barnett is made in the USA so you can order parts just about anywhere.

I run a 831cc KZ650 putting out around 90HP to the wheel with stock clutch/EBC springs and zero slippage.

I'd get new OEM springs, not aftermarket, unless you got a Kung Fu grip.  Lube the clutch cable and release mechanism while you are at it.

Listen to Ness. Plus get the good new motion pro cable.

The EBC replacement springs I mentioned are only a 10% pressure increase, nothing like the performance "red" springs of the past. I run them on all my builds and you can't notice any increase effort at the lever.
10% is only 4lbs per spring X 5 springs = 20 lbs more static pressure on the hat.

The Barnett springs listed there will be stock pressure.

Stock Kawi clutch springs from local dealer are $13 x 5 = $65, Barnett kit is $43, EBC kit is $16 plus they give you a extra spring.

Stock pressure for a 650 spring is 46lbs @ .990" installed height, and ZX6R (2009) are 60lbs @ .990" according to my pressure gauge. I needed to be able to check that stuff for my lockup clutch on the drag bike. You add shim washers to go up or down on hats static pressure (number of springs X LBS)

I sold the "red" springs a lot of years ago, never tested them but they had to be upwards of 90lbs. Not sure what brand, possibly Cir Cycle.

I had those performance springs when I did my first "hot" engine. Back then I didn't know any better and had developed a super strong grip from years of weightlifting. 

I have no idea if you reused the clutch friction plates or if you purchased new ones, but a past owner may have used automotive oil instead of the approved “motorcycle” oil. The massive difference with the automotive style is that they are FULL of additives to reduce friction in metal parts. Those additives will contaminate any wet-style clutch disk and make them slick (surprise)and then they start to slip when power is really applied to them.
I don’t know if this is your issue, but it’s something to be aware of.
The idea of really reducing friction in our air-cooled motors is what draws people into accidentally using automotive oil instead the wet-clutch oil. When I was 16 I put Slick-50 in my Honda cb160.  That was dumb on multiple levels.