83 gpz head 77 650 engine

Does any one know if a 83 gpz head will fit on a 77 650 engine. If so what could I expect performance wise, 10 HP increase?:huh:
Will the chain be the same for the cams. I know that the gpz cams have a longer duration than the stock 77 650 cams. Will my stock 4-1 header fit the gpz head?
what is stock hp of a 83 gpz and how many gears does it have (5 speed or 6 speed)?

If you are talking about a 550 head then I would say no, but just last week I was inquiring about a 650 head on the 750 motor and it was decided that it could work, just might not much good for power.

They will have different cam chains though. The 77 650 will have what looks like a normal bicycle chain where the 83 will most likely have a hi-vo chain.

Hope that helps until someone else can give a better answer.

Are you set against putting the GPZ engine in the KZ650? Seems like less modifications.

Yes, the 83 GPz750 does have a HyVo cam chain, and not a roller chain like the 650, but you can use the 650 sprockets on the GPz750 cams. The GPz750 head is the same as the KZ750 head, except the GPz head has no provision for a tach drive cable (GPz750 cams don't have a tach drive gear because the GPz750 uses an electronic tach).

Stock 83 GPz750 was rated at 85 hp.

Personally, I would not use the GPz750 cams on a 650, as the GPz cams are biased towards high rpm hp and the midrange will suffer. I think a set of KZ750 cams might work well on a 650, along with a KZ750 head. I think you would pick up an additional 5 hp that way.

KZ650 64 hp
KZ750 74 hp
GPz750 85 hp

Mellvis! Is that you? Good to see you back.

wiredgeorge wrote:

Mellvis! Is that you? Good to see you back.

It's me. Thanks for the welcome. I've always been here, just not much going on to talk about.

I had mention before about 750 cams in a 650 and recieved lots of good information. I'm sure the post are still in the archives.

kzrider.com/forum/viewthread.php?tid=11315

This is the link to the 750 cams in a 650 post.
I hope this helps!

Post edited by: mellvis, at: 2005/10/20 11:05

i found this topic during a search and since i can get my hands on a gpz750 head, can you can install the upper idler conversion kit on the head like we do on a 1000 j-head?
i had the conversion done so i can run the j head on my 77 1000.
i want to know if this is possible on the smaller cc bikes as well.
i also had the boss for the tach drilled on the j head so i can run a regular tach.
has anyone performed this swap with success?
just benchtop racing here but won't the big bore kit run better with a stock gpz head then a ported 650 head?

just benchtop racing here but won't the big bore kit run better with a stock gpz head then a ported 650 head?

I don't think Colin would agree to that

Port a 650 head and use the 750 valves and you have a 750 head with a smaller combustion chamber with a higher compression ratio. It just requires more work when you use the 650 head.

i'm trying to drop compression a little.
i have a old mtc 784 kit for my 650 and the pistons are 12.5:1.
way to much for the street.

steell wrote:

just benchtop racing here but won't the big bore kit run better with a stock gpz head then a ported 650 head?

I don't think Colin would agree to that

Port a 650 head and use the 750 valves and you have a 750 head with a smaller combustion chamber with a higher compression ratio. It just requires more work when you use the 650 head.

That's the set up I have on my 650.
As far as putting a 750 head on a 650 with roller chain there's some problems with the roller chain on the 750 head.

650 head with cam chain idler



750 head with no provisions for idler



GPZ intake cam



Yoshimura intake cam, you want to talk duration.



here's a pic of my intake port.



stock port.



Mark

Post edited by: Mark Wing, at: 2007/05/27 20:55

I just bought an 80 Kz750 cylinder block from ebay for $25.00 for my 77 Kz650. I wanted to put the Wiesco 810 in it. I know I have to open the casings on my 77. I was planning on running Kz 750 cams and valves. I would like Midrange power as opposed to top end. What the best setup for that w/ the 810? Should I use the 650 head ported or get a 750 head? Is the compression going to be to high for the street w/ the 650 head ported? Should I mil the heads down at all? What kind of HP increase might I be lookin at w/ the 650 head vs. the 750 head on the whole setup?:blink: Many questions I have Grasshopper...

Post edited by: vach, at: 2007/05/28 00:15