4cyl 750 heads

I agree about spacers not being good for squish, but the turbulance of the boosted incoming charge effectively reduces the need for squish on many turboed engines.
The benifit in reducing CR from say 10:1 to 9:1 and thus being able to run another 5psi far outways any benifit you will have in having a tight squish band.

The 650 bottom end is suprisingly strong though. The 750Turbo is effectively based on it after all. The main strength differences the turbo has are larger transmission bearings and the small rod end bearing being 1mm larger.
You can always upgrade the bolts, as I have done, so the big 8mm cranckcase bolts are ditched for 10mm ones and the long 6mm bolts around the transmission area enlarged to 8mm ones. Its fairly easy to do.
Oh and BTW when you do the bottom end ensure you put a smear of bearing retaining compound on the output shaft bearing and the clutch bearing. I have used Loctite 638 on mine. It stops the bearings spinning in the housing as can happen.
Potentially the weakest thing is probably going to be your cluch itself. The 750Turbo uses an extra plate to help beef it up a bit. You might want to consider making a lock-up. I beleive the KZ900 snowflake will fit the 650, can someone confirm that? So you'd possibly only need to make a spacer to get it under the cover.

i have a gpz head for free if you want it.
shipping is on you though.
it's a bare head and you will need to heli-coil a plug or two but it's free.
if you don't want it, i will offer it to anyone here for just shipping.
i bought it for the valves,shims, buckets and retainers.
so it is a bare head.
ugly as sin and has issues but what the heck, it's free.

I really dont want to push the boost and hp. it will be fine as a low boost setup. like i said, i have the 12 to go fast:woohoo:
I have an APE clutch kit in it with HD springs, im worried about the basket not slip, but having a lock up would be cool. i run an MTC 2 stage lock up on the 12(MTC billet basket, Muzzy hub and sleeve and thicker steels, only thing oem is the fibers lol)

what yr is it kawsakiman? I have kz750 valves and the complete valve train from the 650 head(i think...)
helicoil the spark plug hole?
im interested

not sure but i think it was off an 83-84.
don't quote me.
it does have the mini "bathtub" in the combustion chambers though.
after the battery in the camera charges, i'll snap a couple pictures for you.
you get first dibs but there is also a local guy who wants it.

thx Steve

I think i may wait and look for a good one in summer once i finish my current projects. let the local guy get it. thx though!

kawasakiman you have a pm

leave kawasakiman alone! First I ended up with his tracy body, and now I am getting this fine head! haha!

thanks again for the head I will send a pm to find out when I should come by.


Does anyone know if the mini "bathtub" design added any extra power the the 750's compared to the old round design?

hardr0ck68 wrote:

leave kawasakiman alone! First I ended up with his tracy body, and now I am getting this fine head! haha!

thanks again for the head I will send a pm to find out when I should come by.


Does anyone know if the mini "bathtub" design added any extra power the the 750's compared to the old round design?

Just make sure you dont turn up without that trailer/load of beer you yapped about bringing to sweeten the deal. :laugh: