750/810 stuff

OK got a few questions and some info, first I spent my evening measuring cams, this time with a dial indicator, stock 650 cams are .306 lift 1985 GPZ cams are .327 the old V&H cams are .348, I found both intake and exhaust on all were the same, this means the V&H cams are probably best for stock 750 valve size,.344 lift max according to my investigation, the V&H cams have broader nose and slighly more duration than the GPZ cams... now some questions, 1985 750 head,, I was going to have it milled .025 but after some measuring I find the edge of the intake valve is only.007 from the head surface leading me to believe its already been milled and the head looks like it has,anyone know stock measurements or how far I can go on it, the seat is right on the line now... are there any ways of telling a GPZ head from a KZ750 head, visually or maybe some other way... A cheap degree kit, went to Harbor Freight bought a dial indicator for $7.99 and a base(electromagnetic) $7.99 a degree wheel goes for 12 to 18 bucks(not harbor freight)14mm spark plug gutted with a stud welded in(TDC finder)free total cost about 30 bucks

83-85 GPz750 head has no place for a tach drive and squarish fins compared to the KZ750 head.

When you say the valve seat is only .007" from the head surface, are you talking about the 30* angle or the 45* angle of the seat? The 45* flat is where the valve actually seats, and it's the middle of the three flats, so you can safely mill down to it. The valve is ground at a 45* angle, the seat is ground at 30*, 45*, and 60*, with the 30* angle closest to the surface of the head and the 60* angle closest to the port.

A picture is worth a 1000 words








Ignore the valve seat width specs, they apply to a specific vehicle and not a KZ (may be the same, I haven't checked).


Link to interesting read about valves and flow

with a depth micrometer on the head surface to the edge of the intake valve edge is .007. The 30 degree angle is already been milled into, almost touching the 45 angle... The head and cams I got off internet and the guy said all he knew was it was real fast but sometimes popped through thru exhaust and he was sure it had V&H cams cause he still had the box, so I figure it needs springs, otherwise its in real nice shape, but he didn't answer anymore emails,so I'm trying to figure out what I got

I have a 750 head sitting on the bench that I can measure and maybe we can figure this out.

I can tell you with certainty that if the head has been milled .025" or more the intake valve will be above the surface of the head.

Removing .035 would take it to the edge of the 45* if the seats have never been cut, if the seats have been cut then it might not be possible to mill .035".

The simple way to measure would be a straightedge across the combustion chamber and measure from the straightedge to a specified point in the combustion chamber to determine the depth.

All 750 heads are not the same, I have placed four different 750 heads on a cylinder block, and on none of them were all the combustion chambers located dead center in the cylinder, they were all offset and by varying amounts.

I think I will cc all the combustion chambers to see if they are all the same size. At the moment, I doubt that will be the case




Just re-read your post.

Are you saying the valve is .007" below the surface of the head and doesn't protrude above it?

yes the valve is .007 below he surface but after looking at it again the surface is right on the 45deg cut, I've had other heads cut and this head has the same marks from the surfacing wheel, I really don't think it can be cut anymore than it is, the ports are smooth and the only grind marks in them is around the valve pocket and no ramping around the guide but as for a port job maybe just the pockets or none at all, I have a bunch of 650 heads and one 700 head and this 750 head so for me to compare 750s I can't yet but I know where a bunch of parts bikes are

I've got a customer with an excavator down at a job site that's going to consume most of two days to repair, so I won't be able to do anything till Sunday.
As soon as I can get to it I'll take some measurements and some pics and post the results.

Aluminum heads are generally cut with a fly cutter on a mill and leave faint arcs extending across the head.

I have the arcs accross the head, did auto mech for years had many a head milled, I went and got the 84 700 head, (seems to be a 650 head) and measured surface to valve edge and came up with .036, it has the 650 valves in it but also a much smaller chamber, I'm gonna say this head is already milled I don't see anymore I can take off, I went to the bike shop today and found two GPZ750 parts bikes one is an 84 the other looks the same but I couldn't get to it, didn't have enough time as he was closing up, I will check them out monday throughly

My 82 GPZ750 has a factory ported head, at least as far as I can see down it on both sides. I bought it brand new so its not something that was done to it.

I don't think mine is a GPZ I do know it was an 85 I'm gonna dig out the cc kit and check it

When you cc the head do every chamber, I'm really interested in seeing the variance between chambers.

Here's some measurements I just did that will explain my interest

Distance between surface of head and edge of intake valve: .000", .000", .012", .009".

Distance from surface of head to a point between the valves (greatest distance): .770", .780", .775", .790".

This is a 8o KZ750E cylinder head that has never been milled, and all four of the 750 cylinder heads I have are similar in that none of them are consistent, even the distance between combustion chambers varies, and none of the four heads have all four combustion chambers centered above the cylinders, they all vary.

I was expecting better

Haven't got to do the cc'ing yet but checked out the GPZ is an 84 a bit rough but all there the other one turned out to be a ninja water cooled, there is another 750 twin and two GPZ 550s in the same spot, he says he might have the title for the ZX750 and didn't say how much yet, I've already pulled 1 S1 250, 1 S2 350, 2 S3 400s, a 750 twin, an H1 500 roller and a suzuki GT550 out of this place all part bikes and sorta cheap, gotta be atleast 7 to 800 bikes in the yard

where is this yard? I would not mind a GPZ parts bike.