Mixed Cams

I dropped a GPz intake cam in my KZ750.



One of the things that's kept me from trying these GPz bumpsticks is that the exhaust cam doesn't have a tach drive gear. I scored an electric tach from a Spectre, but haven't gotten it to work yet. I've been running the stock cams in my bike with the K&Ns and Kerker and port & polish. I enjoy a very nice midrange that I don't want to give up.

Trav installed GPz550 cams in his cafed LTD550 when he put in the 615cc pistons. All his power is up in the top end, and he says it's a great rush, but you have to rev the piss out of it. He's in the process of putting his stock exhaust cam back in (he might even have a thread going that I don't know about).

If using just the GPz intake came would open up my top end a bit more without sacrificing too much of my midrange, I was willing to try it. It just never occurred to me to use only one of the cams...















Wanna know the really cool part?

Since I rebuilt the motor a few thousand miles ago, three of my intake valves had closed up to 0 clearance (it was due for a valve adjustment, anyway).

This new cam has a smaller base circle.

My clearances are all within spec now.

I didn't have to change out one damn shim!

I put the cam in and measured everything twice, and it's all within spec. It's like the bike wanted this cam!

My friend calls it "mechanical kismet".



My crazy brother stopped by. He'll be back at noon tomorrow, and we're going for a ride!

I run mixed cams in my GPz1150 and love the combo. I had the same problem with the tach when I went to the 84 GPz head and had to switched to a ZN1100 cluster. The cams I put in were .420 intake and .410 exhaust. The full range power is unbelievable.

otakar wrote:

I run mixed cams in my GPz1150 and love the combo.

I KNOW! :laugh: In my research on this subject, I ran across this:

I would stay wit your original exhaust cam and just change the intake. this will give you a longer power stroke. I did that on my GPz1100. My exhaust is .010 less lift than my Intake. This gives better low end torque.

Also, a friend of mine runs a gixxer intake cam in her Bandit 1200.

The full range power is unbelievable.

I'm about to go find out! My brother just texted me, he'll be here in about an hour. It's 61F and dry, but windy as hell out there.

Here it's 21f and snowing.

Just out of curiosity, what are the spec differences between the 2 cams for this would seem pretty important information.. No?

Example: My .365 Webcams for lobe centering and valve opening/closing overlaps...

according to megacycle

Stock GPZ-750 lift: .354" Duration at .040": 250°


Stock KZ-650 Lift: .308" Duration at .040": 220°



Some info from 750turbo.com

www.postimage.org/image.php?v=aV129aDS

The GPz intake cam has .5mm more lift than the stock KZ cam.

There's more top end rush, yes, but what really surprised me is that my beloved midrange is now enhanced!

In the above video, you can hear a bit of the top end rush kick in before the wind noise overwhelms the audio. I'll shoot some more video, and this time with the microphone covered with some tape, but it might be a week or two. Yesterday was the last of the nice weather for a while, forecast calls for a bad winter storm...

hmmm, the vimeo link doesn't seem to work...

Did u here back from your bud Tray and his 550 cam experiment yet?
I would love to here if there is a dif if u put the matching GPZ cam exht in.
U made some gains by putting a larger intake cam in. that makes perfect sense.u allways do when u alow the motor to breath better.
I am curious to here the dif ,when u just change the exht cam, from the same size to smaller and back again.
I have heard about using a smaller exht, but never heard of a big gain?

Main reason is the curtain area. When the lift is enough the throat is the limit on the flow. The smaller exhaust valve does not need to lift as much as the larger intake before this occurs.

But this mostly applies to big cams and all out motors.
I am very interested in learning more on this subject. can anyone help out hear?

Wow, I haven't been on here in forever!

Mark, I think you might be misunderstanding a bit.. or I'm misunderstanding you! The matching GPz exhaust cam will definitely bring a gain. That's actually what I have in my engine now. Matching GPz550 cams. Basically, it makes my engine more like, if not almost identical to a GPz550. It's nothing radical, just a differently tuned setup for the engine.

The thing is, the way the GPz is tuned.. well, it's the forebearer of the zx6r. A hot bike at the time, it was the most 'race-replica' you could buy from the factory, back in the day. However, that really didn't mean much more than more compression, larger intake valves, and most dramatically, the cams. Haveing these cams gives the engine more peak hp, but it's all way up at high rpm and high speed.

I remeber what the bike was like to ride stock. It did have plenty of oomph, but especially for a young guy getting comfortable on his first bike, it soon seemed to need 'more'.. So I put in some GPz cams, and so on.

Partially on a hunch and out of curiosity, and partially out of a seeming paradigm shift I've had as to what is actaully an 'improvement', I've decided to see what would happen mixing the cams, as GG has already done. It seems like the results speak for themselves! I'm just curious what it will be like going from both 'hot' cams to the middle-ground, so to speak. I also wonder if a 600 will respond less favorably than a 750.

We'll see.. I've been working on a few other projects at the moment, and it's 21 degress out!