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The Cruising Gunsmith
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I hesitate to tempt Satan's minions by saying this, but I got my 1979 KZ750 back together again last weekend and it is running really well..... of course, I said the same thing after the FIRST overhaul back in October and then the cylinder base gasket disintegrated and I had to tear it all down again and start over.

Hopefully, it's buffed up for another good run of miles.

Thanks to all who provided information and moral support, Rich especially.

For all, here are some lessons learned ... the hard way:

1) Athena gasket sets suck but you may have to live with one. The head gasket is OK, at least seems to be so far. The valve cover gasket was basically pressed cardboard and was warped. It didn't last long.

The cylinder base gasket was pressed fiber.... and it apparrently was unable to stand the crushing pressure from torqueing the head down. It disintegrated almost immediately after running. I got in about 200 miles before the cylinder shifted on the base enough to lose compression (game over, had to tear it all down again). Made a new base gasket from gasket material and it seems to be solid enough.

The oil pump housing gasket was actually too think, that dimension is a critical one to determine oil pressure. I used the gasket from the previous head rebuild gasket set (still had it) which was the proper thickness.

2) Use the black ultra high temp RTV to seal the critical gaskets.

3) Piston rod end clips: the ones that came with the new pistons have little "ears" to help squeeze them... very convenient but they don't let the clip seat fully in the groove and also the pin puts pressure on the clip ear. The pins are designed to have a bit of play end to end, those clips don't fit right. use Kawi OEM clips without the ears or clip the ears off.

4) Piston rings: managed to break an oil ring trying to put it together the second time, I still don't know how. I assume the ring hooked an end on the groove edge and then the compresor squeezed it and it popped. I recommend compressing the collar with fingers only until all rings are deep in the grooves and then apply the clamping tool.

5) You probably don't need valve guides. I bought a new set figuring 75k miles and they would be toast, but none showed any wear. The head guy said they usually don't unless the valve is angled and applying side force to the guide.

6) SHIMS: a good machine shop is your best friend. With 32mm shims as rare as honest politicians, I gave the shop an exact set of +/- tolerances on the valve end height to stay in tange of the four shim sizes available and they kept the valve ends within target.

So it cost about twice as much as I thought it would and took three times as long.... but it's done now and life is good again.

Except, of course, our string of beautiful weather has suddenly ended and we are seeing rain.:mad:
 

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But you're in California, it'll get better!

Glad the work is done, and sorry you had to learn things the hard way, but now you're part of the do-it-over club!

Hopefully I will get mine together soon, and I can ride also.
 

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The Cruising Gunsmith
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Discussion Starter #3
But you're in California, it'll get better!

Glad the work is done, and sorry you had to learn things the hard way, but now you're part of the do-it-over club!
I wouldn't be bitter if it had been my screw up, but that brand new cylinder gasket just disintegrated.... and I was sick to my stomach watching it after all that work because I knew it meant I had to do it all over.

Oh, well.... I'm sure I grew as a person.
 

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I'm glad you grew, I seemed to have regressed as I build mine! I haven't thrown fits like this since I was probably a year old!
 

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The shims have been the fun part. All of the exhaust side were at 0 tolerances. So we buy .015 over to fit. Wrong. They must have never been adjusted in their lifetime. The .015 only got us to .0003. So waiting on more shims!
 

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The Cruising Gunsmith
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Discussion Starter #7
The shims have been the fun part. All of the exhaust side were at 0 tolerances. So we buy .015 over to fit. Wrong. They must have never been adjusted in their lifetime. The .015 only got us to .0003. So waiting on more shims!
The shims were what scared me the most. Z1 Enterprises had some in the range of about 260 to 280, and I had the four in the bike which were pretty much the same.

I handed the machine shop the head, a full set of new valves, and explained my plight: he had to lap the seats and fit the new valves so the ends were "in range" of the availabe shims. On each valve (based on the existing shim) I gave him the "over under" range for the finished valve height, and the total range was about .010".

he got every one in range, which kind of amazed me. That's some pretty accurate machine work.

I set them leaning "loose" (about .003" to .005") the spec is .002 to .004.
 

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Looks like you found a good machine shop! And loose it ALWAYS better than tight. This is a MOTOR we're talking about, remember :mrgreen:
 

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The Cruising Gunsmith
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Discussion Starter #9
Looks like you found a good machine shop! And loose it ALWAYS better than tight. This is a MOTOR we're talking about, remember :mrgreen:
I went to the dealer where I bought the bike and pried the name of the machine shop THEY use for their work out of the manager. Top notch shop that builds racing engines and does regular work too. That's about the only thing on the project that went right.
 

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I tried that at work. Most people would look at me and say, "Now, really, where do you take it to?" They would take it someplace else, and then come back and complain that it wasn't done right. There's no helping some people.
 
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