KZ750 cylinders and head specs (tolerance)

Hi,
In my original kawasaki service manual i don't see the specifications regarding cylinder block height and head height measurements.

I would like to know by how much the engine has been milled from original specs!

My cylinder block reading TOP to BOTTOM (76.06MM,2.9945 inch)
Head readings TOP to BOTTOM (105.04MM,4.1355 inch)

Do i need cam timing adjustment?


Best regards,
laurent

Even on google looking for KZ750 (GPZ) 1982 head thickness didn't give any relevant result!

How do you guys know your head/block as been milled X amount (from original)?

laurent

What you really need to do is figure the Static compression ratio. You need to find the CC of your combustion chamber in the head, and how much the Piston volume is. The piston volume will be from your supplier, or you can also measure that. Go to this link as it has a calculator for it.
www.rbracing-rsr.com/compstaticcalc.html

Timing aside, nobody measure head/block «thickness» ?
Why going through head chamber cc and piston cc measurement to know if head/block is stock ?
I know that you can by this way but isn't all the heads/engine (same model) from kawasaki factory (stock) the same height ?

Clueless...

thanks for your reply
laurent

I just want to quickly know if i can run stock cam timings... the company who milled the head is not clear how much they removed...

I looked around and found this and copied/ paste for you to read.
"The 82 GPz750 has a combustion chamber volume of 24.9 cc which is very good. The 83-85 GPz750 have chamber volumes of 25.9 cc . The Kz750 H 24.8cc and Kz750 L 25.3 cc. You can easily switch these heads between motors."
So if you CC your head, then you should get a volume # and see how close it is to stock. Static compression will be different than actual Dynamic compression, do to Camshafts/ altitude, etc.
Only assembly and checking the degree of the cams will tell you where they are against the setting called for.

Sorry this is where I got it: members.tripod.com/gpz_rider/technical/FAQ2000.htm

Thanks for the info Motor Head!

see how close it is to stock.

Do you know the tolerance before it needs cam timing work?

I don't have access to the tools to do cam timing. It would be great if i could know if engine is plug and play or plug and pray!

People says (from the forum) less than 0.008 milled (total)is nothing and doesn't required a cam timing job. I can live with a few degree retarded timings (i don't mind performance) but i think that too much can be fatal to an engine...

regards,
laurent

Things like wear on the sprockets, chain, guides, will all effect it. Only an assembly and degreeing will tell you. Degree wheels are pretty cheap, like $25. A dial indicator about the same. There is plenty of how to degree info on here and all over the web. Slot your gears and set it to spec once the motor is mocked up, or fully assembled if stock cams.

Thanks again!

One more thing:

advancing the cam will increase low speed torque, retarding the cam will increase high speed HP and torque

Is that statement true or its just BS?

best regards,
laurent

Well that statement looks like for a single cam design, but is the general consensus. Retard to far and you will really loose Idle and bottom torque. Depending on how a cam is ground, it may already have late IN valve closing.

Well that statement looks like for a single cam design, but is the general consensus. Retard to far and you will really loose Idle and bottom torque. Depending on how a cam is ground, it may already have late IN valve closing.

It's not that i want to cut corners but i'm really tempted to put everything back and start the engine to see if it runs. I'm starting to get depressed!
it all started with a scratched cylinder ... then afterward (figured out)i need to paid for a oversize kit..plus machining... the bill are high plus i'm in the middle of the riding season right now and never rode my bike since last year!

What could be the worst case scenario?

Engine was running fine last year even with a scratched cylinder (so i guess timing was right)

The machinist told me he just refreshed the head ...

could cam timing really go wrong at the point of ruining my engine with just a refreshed head?

Time and money (blown my budget real hard... $1500 spent!) are now a real restriction... and my moral took a hit too!


best regards,
laurent

Yea I read your posts, and most would agree to reassemble and ride it. Cam timing is probably only retarded a few degrees, but who knows without checking? But it will most likely run just fine, maybe a bit more top RPM.