Camshaft Differences With Valve Adjustment

Hey gang - Here is an update on the camshaft changes I am making to my 650/810

Last week I blew out the tach gear on the Kz750 exhaust cam in my 810 The third camchain adjuster I put in wasn't up to snuff and I finally decided to go with the APE manual tensioner from Z1 Enterprises.

I decided with replacing the cams that I would go with the hotter Gpz750 cams for more grunt. They have a higher lift and more duration than the Kz750's and are the main reason the Gpz750 had more power than the Kz750. They do not have a tach drive as the Gpz had an electronic tach.

I was lucky enough to have kawasakiman (Steve) set me up with a set of Gpz cams he had. Thanks Steve:)

I had posted a message asking about thoughts on what the difference on valve shimming might be and today I had a chance to start the cam installation. After pulling the old cams and installing the new ones for a trial fitting I checked the clearance and was puzzled at my findings.

DKMK (Dave) stopped by with his extra shim kit and he lent his experienced eye to the job where we measured the cam chain for wear and found it within factory tolerances. Thanks Dave:)

My spidey scenses told me I should pull the head to check to see if I had a bent valve from when the camchain jumped a couple of teeth and the tach drive blew out and tonight

I brought the head and new cams over to my friend's place. He's a bike mechanic and has a '77 Kz650 streetfighter and a Z1 that has run a best time of 9.2 in the 1/4 mile, so he is pretty good with the old Kz's.

I checked for leaks by spraying brake clean fluid into each of the runners and found no leaks, therefore the valves were sealing fine but when I put the new Gpz cams in the 650 head I was surprised how much daylight I could see between the bottom of the cam lobe and the bucket. So my hunch on valve clearances was right.

I ended up having to put in thicker shims in the 0.35 range on all valves. The base of the cam lobes on the Gpz are a lot less meaty than the Kz750 cams. Now all of my clearances are in the 0.10-0.15 mm range, right where they should be.

Tomorrow if I can squeez a couple of hours in the garage, I am going to button everything up including plugging the tach cable to ensure it doesn't leak. It will take a little getting used to running without a tach but I figure I know the sound of this engine so well by now that I can live with just a redline shift light.

I'll keep everyone posted on the performance upgrade with the Gpz cams.

Cheers-Colin Firth-Ontario Canada

Post edited by: reborn650, at: 2007/05/06 01:42

What year motor did the cams come out of?

Hey Steell - Kawasakiman pulled them from a 784 motor he picked up on ebay. Can't say for certain the exact year of the cams but I am fairly confident they are from the '83-'85 Gpz given the considerably thicker valve shims I had to swap in to get the valves within spec.

If thenew Gpz cams were the milder '82 Gpz cams I don't think that there would have been that much of a difference between the existing valve settings I had for my Kz750 cams.

From what I have learned, the '83-'85 Gpz cams have 0.05 more lift and duration than the Kz cams. The Gpz cams also have a little more lift than the aftermarket Andrew Kz cams.

Cheers-Colin Firth-Ontario Canada

Post edited by: reborn650, at: 2007/05/06 11:11

lets see if i can shed some light here.

the cams were for a 84 gpz 750.

Thanks kawasakiman (Steve) for clarifying this.

Cheers-Colin Firth

Just building a database for future info

For some reason all the GPz750 motors I have had were 83 models, and I am not aware of anyone have the excessive clearance problem.

But I have read that some GPz750 cams had a smaller base circle, and I was just wondering what ones.