Gpz 750 head is bowed slightly

I'll check into that. I am very upset right now with Arnold Motor supply. Went to get my valves, springs, tappets, retainers for my head, and my cylinder block with new manual tensioner, and no one knows where they are at, they can't get a hold of the guy that dealt with me their because he went on vacation. We looked all over the building for over a half hour. Talk about a joke. So gave them until tomorrow at noon before I file a report and go from there.

They found my parts. Ordered the studs and nuts from APE. Those should help my situation. Thanks for all the advice again.

Hello again,

[strike]As far as I know (disclaimer here), the Spectre has the same combustion chamber (and basic head casting) as the following: all 1980 - 1982 750 fours, all 1983 four cylinder models except the GPz750[/strike]. WRONG! See my latest pos... But I am no expert when it comes to the smaller fours (Correct!) - I've never owned one, and have only wrenched on a few for others. I'm relaying what I've heard and read (with reliable sources - owners, racers, and K brand service manuals).

The 82 GPz uses the same basic head casting, but with racier cams. I don't know if the 82 GPz had bigger valves than the rest, but in Kawasaki tradition, it would seem likely. [strike]The somewhat hot-rod 82 GPz engine continued on as the 750 "L" sports models in 83 and 84. They have the familiar "hemi" combustion chamber vs. the 83 and later GPz style "bathtub" chambers.[/strike] - WRONG AGAIN! I think the hemi chambers will work on all model pistons, but bolting on a bathtub head onto hemi pistons might be a problem.

Yes, I know there are no CAM BEARING INSERTS in the smaller four heads! Duh - huh. But there are still CAM BEARINGS! They are integrally machined into the head and bearing caps. Cams don't just levitate and wander around around in the head...at least not by OEM design they don't.

Other than the K brand big fours, I don't know of any other Japanese 4 and more cylinder engines that uses cam bearing inserts...I've only seen KZ1300's from the outside, being heavyweight water pumpers and all I avoided those.

If your integral cam bearings show signs of metal to metal contact with the cams, then "bolting down the head" in the hope it will straighten itself out might have about a rowboat's chance of crossing the North Atlantic in December....or is that Deluxe First Class tickets on a big ship's maiden voyage Europe to New York in April, 1912? I'm saying the odds are not in your favor.

Who did you speak with at APE? Did you tell them that you think the head was warped 1/32" at both ends and also dished in the center? Did they know your cam bearings have signs that the cams are binding in them? Before making a bad decision, check the cam bearings first. If they are ok, then have the head properly measured for flatness and properly recorded in thousandths of an inch (not fractions) - both where (on the head I mean) and how much out of true it is so it can properly be evaluated. If the cams aren't rubbing, and it is only warped a few thou in only a couple of places, then just bolting it down will probably work...

Oh - be very careful about taking bike parts to an automotive shop for machining! I have seen Chevy valve keepers placed in KZ valve retainers (no - they don't fit), valve stem tips ground below minimum specs, installed valve heights way out of spec, valve shims hopelessly mixed up, inner valve springs left out, valve springs installed upside down, exhaust studs milled accidentally, parts lost or mixed up, bolts lost or the wrong bolts substituted, metric threads chased out with standard taps, etc.

Make sure you provide the shop with copies of the relevant pages from the Kawasaki manual on how to cut the valves and seats, install the valves, machine the head and cylinders, etc...or you might have trouble....

BTW - a bit of a resume - I worked in a racing automotive machine shop for a number of years back in the 90's. I was the master machinist there for racing engine blocks, heads, rods, pistons, cranks, and anything else that had to fit together properly to work. Not one of the hundreds of engines I machined ever had a failure caused by my work - not one. A few of the engines that came out of our shop set NHRA records and won championships in dirt track and sprint cars...the last engines I machined there helped to launch a career for a guy named Garry Chomiski (Google it). The engines we built for him were 292 - 410 C.I. SBC's (no one should try to tell me "Chebbies" didn't come in those sizes - these were not stock station wagon engines, not even close!) that often revved to 11,500 rpm and generally made 2.4 HP per cubic inch normally aspirated...

-Scott

Kray-Z is correct, the 1982 gpz750 head is cosmetically identical to the Spectre and Unitrac gpz750 heads but they are not all the same.
The 1982 gpz750 head was hand ported from straight from the factory. Beyond that, nothing about it is different from the Spectre. It uses the same cams as the kz750e, LTD, Spectre and even the Zephyr 750's made in the 90's.
The Unitrac gpz/zx750 heads are not factory ported but have much hotter cams and redesigned exhaust valve seats that make putting non-zx750 exhaust cams in a potential pain to shim.
So they all look identical, have the same size valves and bathtub combustion chambers, will bolt up to other 750 motors but they all have other variations that can be a benefit or a hinderance.

On my kz750e, the area of the cam chain tunnel (where they internally bolt together) on both the cylinder block and head were warped upwards. So when I rested the head on the cylinder block with no head gasket, it teetered back and forth on the raised areas so badly, I could fit a quarter in the gap. The combination of the raised areas created a very large discrepancy but it was not a true measure of its total "flatness". Once I had a small amount skimmed from the deck of both block and head they sat perfectly flush.
Maybe the warpage at the ends of the cam chain tunnel can be pulled flat by simply re-tourqing the head. And even though I had them machined flat, there is nothing to keep them from warping in the exact same area again. Only time will tell.

OK - did not see the pics of your head off the bike before now - my bad...it is definitely the later GPz style "bathtub" combustion chamber head. I'm going to guess it is a late 83 model Spectre 750 you have. I've been checking photos on-line and Kawasaki must have switched the cruiser 750 head castings during production sometime in the 83 model year, as I can't find any pics of pre 83 heads with the bathtub chambers (not even the 82 GPz - R1). So you would need to buy one of those later heads if you were to replace yours...still available in the $150 - $200 range, but the more you spend, chances are you will get a better part. I can't see APE making any kind of profit on taking the time to oven or press straighten any head for less than $150. Be careful on evil - bay, I see some that have broken intake bolts and other tough to fix issues the seller doesn't note in the description...out of the frying pan, into the fire...

-Scott

When going through my 750 I don't remember checking the head and cylinder flatness. Maybe that's for the better. Ignorance is bliss! I do believe Jay from Ape regardless though; I've read posts by him more than once telling people to just torque the head down and it will flatten. I suppose there is a limit to everything though.

One thing I do remember about rebuilding my engine is how poorly the valve seats were finished. I used a 45* Neeway cutter on the seat, kissing super light so the seating area would be highlighted, and I was shocked to see how the margin varied around the periphery. The seat margin was literally twice as thick on one side vs the other. I had a 75 degree cutter, previously purchased for reworking a Suzuki GS1000 head, and by a stroke of pure luck it fit perfectly down into the Kawasaki ports and allowed me to true up the seats. Moral of the story is to be careful to check your valve seats. I had my valves centerless ground too and the tech was surprised by how out of true they were. Hate to say it, but I don't think Kawasaki build quality was all that great back then.

Three angle valve seat grind.
Steve

Wow - learning new stuff can be a rewarding exercise - or at least I can tell myself that...

Researching Partzilla head casting OEM part numbers and applications, I find some things very interesting:

The 82 - 83 750 Spectre apparently used a different head casting than the 80 - 83 750 LTD and E models, (which used a 650 style head). No other KZ models shared the same part number head assembly as the 750 Spectre ( that could be because of the unusual paint color, though). All the Spectres apparently used the "bathtub" shaped Combustion Chamber (C/C).

The Spectres got the "bathtub" shape C/C head one year before the 83 GPz750 (the first Unitrak model) and the sport model 750L's received the improved head. That is amazing!

The 82 GPz750's part number is unique to that model and is the old Hemi shape C/C. Probably unique P/N because of the "hand porting" and no tach drive. BTW - don't believe Kawasaki's claim to have done this with every 82 GPz built - I have a virgin Canadian model 83 GPz1100 head, taken from a low mileage wrecked bike, that was supposed to have been factory hand ported, and it definitely isn't!).

A look through all the models from 83 - 84 and up show that the 84 "ZN" LTD, sport "L", 83 Spectre, and GPz 750's got versions of the "bathtub", while the 84 sport KZ700A1 seems to have still received a Hemi head by the part number, but that is inconsistent with the compression ratio of 9.7:1 for that engine and the other visibly updated engine components, so I would say it is a safe bet those engines had the bathtub C/C as well in 84. And here I had always been told the 83 and up sport 700A's /750L's used a non - ported copy of the 82 GPz engine. So basically I think the Spectre in 82, and only the Spectre, sport 750L, and GPz in 83, and anything 700 / 750 built 84 and later had the bathtub C/C.

But of course, I could be wrong (disclaimer)...

And I though the 900/1000/1100's were tough enough to keep track of...

-Scott

All I know is my Vins on bike and engine match and say June of 1982 N1. It is titled as an 83 though. And the pictures of my head are posted in this topic. I've heard the cylinder blocks and pistons are higher compression, therefore different sizes too. I was under the impression they put the straight up gpzs motors in the N1 and N2, with slight differences. I'll post a picture of my pistons and head again. My valves are seating just fine so not going to have a bike shop touch that at this time. I believe my culprit was only the head gasket gave way, and head lost torque. So just going to wire wheel the valves, everything else is cleaned up, did a slight hone, rings everything looks great yet, and put it all back together and hope for good equal compression and vacuum. I did just spend $170 on the hardened APE studs and nuts so I can get extra torque if need be, and don't have to worry about this same issue again more than likely. I bought an oem nos head gasket, and a vesrah gasket set for the rest. I did get to good valve seals also. So hoping I won't have to take anything apart again until a re ring or big bore kit and do a valve job at that time also is i still have the bike. Keeping my eye open next for the kz 1000 with the cool rear spoiler. And build that motor up. This bike is nice and will keep her clean in proper order until then. Valves will be done to specs like the manual says to do. And a 3 angle seat grinder would be the tool I'm sure Steve. Scott, and everyone, comments are always appreciate and the discussion.

These are specs from my manual. 9.5 compression ratio.

Kawasaki constantly evolved the engine starting in the 650 days. I believe the Spectre was the first to get the new head and pistons with thinner rings. Cam lost the mechanical tach drive. Not sure about lift and duration on the cams. The Spectre kept the Keihin carbs, whereas the R1 went with the Mikuni's. Just some small detail changes. Oh, and the engine got the squared off fins too.

Thanks everyone.

All info that I've gained from this thread will come in very handy when I (eventually) go shopping for a sporting 750. I originally thought an 82 GPz was my best choice as it has the fairing, but I'm leaning toward the 83 and newer L or A model now because of the newer engine design...and I still get Eddie Lawson Replica looks w/o the premium price tag...

-Scott