Z750 Engine Rebuild - by a total amateur!

To me it looks like a UK model as US had removable breathers on the front top of the cam cover. Going off your engine number it looks like an early model KZ750e about 1980 E1…. Explains the early cam chain tensioner. The 738 on the side of the barrels denotes the engine size, that’s normal for the balancer to have various amounts of dimples and the amount of slack in the cam chain is common, you need to asses it by measuring the length between a certain amount of links.

Also the pic of the head chambers if I am correct seems that 2 of the cylinders may have suspect oil rings hence the wet look (oil soaked). To asses the condition of the head and valves you need to remove them and check it that way…. worn seats, bent valves, scoring etc is easier to gauge when disassembled.

Tip; when you remove the pistons check the scuffmarks on the side of the skirts you can learn a lot about them that way…. If the scuffs are not vertical to the piston for example you may have a bent rod in that cylinder, then you need to check if that barrel is not out of round also… and so on.
Pulling a motor apart can tell you a story about its history…



If you just know what to look for!

Cheers for the info guys.

The cylinders are dry as are the valve chambers (underside of the head). The wet look on top of some of the pistons is actually moisture - I suspect the engine has been standing in a damp garage for a few years.

The plan for this motor is to install a Wiseco 810cc piston kit I've ordered which naturally means new rings all around and a rebore / skim if needed.

The cams are sound - smooth with no scoring or discolouration as with the cam caps. Cam sprocket teeth are nice and fat.

I'll remove the valve assemblies and store in labelled boxes then the head, barrels and block are all off to be blasted and stove enamelled. I did want to do the headwork (valve clearance, checks etc) myself but I've decided the machine shop will also do that so it will get a comprehensive check over and get new seats if needed, new valve seals and shimmed up correctly etc etc.

Cam and primary chain will be replaced unless they are damn near close to new factory measurements.

The stuff in the oil filter strainer I don't know - could be bits of old gasket...

The carbs are my real issue as I don't want to open them at all.

Is it worth fitting a modern tensioner? Any other 'upgrades' to do now?

Okay.

Made a bit more headway last weekend and got the all the valve assemblies out and into organized storage.

I didn't even know how to use a valve compressor but a bit of YouTube and away you go. Valves compressed, keepers lifted out and everything slides out - one job that went as smooth as it should have done!





Now came to take the barrels off. This thing did not want to budge. It was seriously corroded on there plus a lick of paint and extra crud just locked it on. The head cam off real easy but this went nowhere after ages of gentle tapping and shifting. Couldn't even slide anything in there to crack it open.

I damaged one fin as I increased the rubber mallet action and that opened the floodgates.

I started whacking the shit out if it and destroyed the f***er getting it off!




Pistons...




Closer look at the engine bolts show how corroded with crap they are - worth keeping or upgrading to ARP?





Anyway.


What I'd love to do this weekend is get the pistons out, crank out and spilt the cases. What do I attack next? Oil Pump? Do I disconnect the conrods from the crank first?


Clutch pressure plate off and friction plates out. - Special holding tool in full effect!




The plates measure between 4.0mm and 3.9mm. Is this a decent thickness?




Clutch holding tool in full effect - the big bolt holding the clutch basket on came off pretty easily - thought it was supposed to be super tight?





Also, the 17mm nut was really damaged. Big gouges in it and and a bit chewed off???




No sign of any rubber - I thought an important part of the whole clutch mechanism is the condition of certain damping rubber parts here...?


Oil pump came out easily - how do I check if it's in good condition? I destroyed the mesh trying to pry it out - are those replaceable?




I thought the 3 crosshead screws were holding the pump in but it came out just taking 2 off - the other is totally ruined and stuck in.




So, down to the bottom cases with the crank, pistons and gearbox to come out now and then I can start getting things blasted and cleaned up.

What do I attack now lads?

Looks like a fun project!

I think most of the 750 engines are pretty much based on the 650 etc. Here's a link to another version of the bike called the ZR-7 here in the States: www.zr-7.com and their forum: www.riderforums.com/forumdisplay.php?f=37
If you dig deep enough, you'll find a link to the factory service manual in .pdf format.
jadz.com/postfiles/ZR-7S%20Motorcycle%20...0Fifth%20Edition.pdf

Cheers!

Philip
'00 Kawasaki ZR750

bloody happy new yr mate !!!!thanx for the pics...one amateur to another...lol planning on pullin my valve cover to stop some oil leaks & inspect.good luck with your bad motor scooter. ace

royalratch wrote:

So, down to the bottom cases with the crank, pistons and gearbox to come out now and then I can start getting things blasted and cleaned up.

What do I attack now lads?

Next step is to get that bolt in the pic out, remove the bracket, remove the cap on the opposite side of the engine, tap out the secondary shaft and pull the starter clutch assy, then you're ready to split the cases.


Btw, the clutch hub nut (the one holding the clutch hub and basket) should be real tight - by the look of it I'd say it has been chiseled off at one point and not torqued properly when reainstalled, you should replace it with a new one.

98 ft-lbs for the clutch basket gland nut. That's tight...

66.6mm bore might be out of serivice limits on the cyl block.

If that's the case, why do they offer these pistons for this model engine exactly - and is a common mod?

BOO... HISS... Very bad cylinder block removal!

The destruction of that block was completely unnecessary.
Maybe you should pick up a service manual :dry:

You'll need it for all the specs anyways... someone here looking at a picture and say "yeah, it looks fine use it" is just nuts. Everything needs to be spec'd properly for wear.

Which I'm presuming you know, and were going to be doing anyways after your teardown. :huh:

You need a good hand impact to remove stubborn screws.

Good luck, and don't break anything else! Makes me sick to my stomach.

TeK9iNe wrote:

BOO... HISS... Very bad cylinder block removal!

The destruction of that block was completely unnecessary.
Maybe you should pick up a service manual :dry: ...Good luck, and don't break anything else! Makes me sick to my stomach.

Nah, he doesn't need a service manual, penetrating oil, or even wrenches. All he needs is the following amateur disassembly tool:

Amateur Disassembly Tool

all i have to say is wow. this thread has as many views as the forum rules....lol:laugh:

650ed wrote:

TeK9iNe wrote:

BOO... HISS... Very bad cylinder block removal!

The destruction of that block was completely unnecessary.
Maybe you should pick up a service manual :dry: ...Good luck, and don't break anything else! Makes me sick to my stomach.

Nah, he doesn't need a service manual, penetrating oil, or even wrenches. All he needs is the following amateur disassembly tool:

Amateur Disassembly Tool

:laugh: :woohoo: :laugh:

Nice...

Well, its a good thing he added the "by a total amateur!" in the header, couse otherwise I'd be pretty pissed.

Sorry royalratch, but newbies should expect some flak! :laugh: We love the pics and love to help too, but breaking things... dont get too much love! :laugh: