TOPIC:

Hi,

I’m looking to get a set of racing cams for a GPZ/KZ750 but they are very expensive.
Has anyone tried to fit cams from newer bikes that will fit the KZ engine?

KR
Sixten

Here are a couple of choices. APE hardwelds and regrinds your old cams.

kzzone.com/cams.html

I suspect the only newer cams that will fit the engine would be from the Zephyrs, and are likely no more performance oriented than the basic KZ cams.

If you are unable or unwilling to spend the money for new or reground cams, the only other option is to carefully watch fleabay or forums like this for a decent set of used cams. You will likely have to be very patient.

I just figured all newer performance bikes probably uses 4 valve heads so I might have to look into getting grinded cams.
Thank you

Yes, and all modern sport bikes have the cam chain on the end of the crank instead if in the middle.

The GPz cams have more lift and duration, than the KZ cams.  You will loose the mechanical cam drive, though.  

You mentioned racing cams. Are you building a full race, track only bike?

What is your goal? Be honest in your assessment of how you will actually ride the bike, that way you can make good decisions about cams, carbs, pistons, exhaust and such. Really radical cams will require aftermarket pistons to prevent the valves from smashing into them. Bigger carbs, a ported head and racing exhaust system will be needed to take advantage of all that lift and duration. That sort of build will be a pain to ride on the street.

If you want a slightly quicker, reliable, easy to ride street bike, the GPz cams with a better exhaust system may be just the ticket. Some bigger bore pistons with a bit higher compression ratio can make a noticeable improvement.

To get "real" performance you need to look at something in the range of .370-.400" lift especially if you have a GPZ head, only the big valve GPZ head will benefit from the higher lift (over the smaller valved KZ750)

Used market value on high performance cams for the smaller engines is around $400-450 a set as regrinds are $800-850 without tax.

The valves are the same for all the 750's, including the Zephr and Turbo.  There is a bath tub combustion chamber head, which may be worth acquiring if big HP is the goal.  

Nessism wrote:

The valves are the same for all the 750's, including the Zephr and Turbo.  There is a bath tub combustion chamber head, which may be worth acquiring if big HP is the goal.  

 

Its not the first time I have made that mistake. I guess I am always thinking about the smaller valves on the 650.

I recently bought some used Yoshi Stage 2 cams .380"/.400" lift for the 650/750 for $425

It’s for racing so I’m only looking for power over 7000 rpm. I have a Wiseco 810cc engine in the bike now with GPZ cams but I’m building a 750 engine out of old parts to ride in a 750cc class. I could take the GPZ cams from the 810 engine but it would be nice to have that engine as a “complete spare engine”. So I’m looking for real racing cams for the 750 engine.
It will have have around 11:1 compression, mild ported head, 4-1 exhaust and big carbs so i think i should use maybe a “medium” racing cam?

Sixten wrote:

It’s for racing so I’m only looking for power over 7000 rpm. I have a Wiseco 810cc engine in the bike now with GPZ cams but I’m building a 750 engine out of old parts to ride in a 750cc class. I could take the GPZ cams from the 810 engine but it would be nice to have that engine as a “complete spare engine”. So I’m looking for real racing cams for the 750 engine.
It will have have around 11:1 compression, mild ported head, 4-1 exhaust and big carbs so i think i should use maybe a “medium” racing cam?




 

WebCam grind #110 looks good :



That is a typical road race cam with power coming on at 6-7K
You probably can't use stock pistons (valve pockets) but if its being built for 750 class limit you will need to run a +.50 mm over size piston to get max CC
Not sure what the rules are on carbs (round or flat slide) but you probably want to run a 33-34 mm throat

I am running similar cams in my 831cc street engine with a big valve 650 ported head and RS34 carbs


 

Thanks for the advice. Im planning to use GPZ pistons. Maybe I have to open the valve pockets a bit more.
I was thinking about just grinding a set of GPZ cams without welding. Would that still require hardening? 
otherwise that would be much cheaper I guess then welding.