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Katit's 1978 KZ650 project 30 Dec 2020 21:23 #840892

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It's time to start my own build thread. Background - lot's of car work, but first motorcycle. A lot of 2-cycle experience racing go karts 25 years ago. So not new to motorcycle engines but new to this one and whole "restoration" thing. I wanted something I like (in addition to my main bike) and can work on. 78 is my BD year, that's why I picked this KZ after some research.

Looked mostly original, parked outside for 1.5 years but ran before that. Bought it from son of original owner. His story was:
2 years ago he paid to make it run. New tires, carb work, some electrical work, new battery. Then he rode it for a season and parked.

First when I got it - I wanted to make it run. When I picked it up I found another 650C 79 for $100 that I picked up for parts.

Posted somewhere here that I got it running but poorly on 3 cylinders. I had to hear it. Then I decided (and because of all of the advice here) to do basic maintenance. But either way - my goal is to get it running first and then start on restoration.

Today I realized that it IS a "PROJECT". More on that later. I saw some "hints", but now it's getting worse.

1. New battery. Yes, it's new. But wrong size. So battery box was unbolted and then bigger battery squeezed in. It's AGM, I was able to charge it and it cranks no problem.

2. Ignition. Points worn. One coil was bad. New Dyna ignition/coil on order. Along with new plugs/wires/caps. Screws on points were worn. Hack mechanic job. One coil was mounted with about 20 lock washers instead of spacer, you get a picture.

3. Carbs. I did not take them out/apart yet. Ordered bunch of parts I knew I need but visual inspection shows cracked boots and mounts(I do have airbox). Zip ties instead of springs. Worm clamps instead of factory bolt clamps. Who know what else I will find in this "carb job". But all intakes and airbox tubes ordered.

4. Valve gap check. I got a gasket and thought OK, lets' get it checked and out of the way. First cover bolts coming out blue silicone. Pretty fresh, so it is same "service" that was done 2 years ago. Of course no gasket. And then I see cam lobes - no wear and all clean inside so I start hoping this is it. NOPE.

See pics. 3 bolts loose, threads gone. About 4 bolts SAE? With finer thread. This SUX big time. Looks like I am into more than expected.

Questions so far:
Do all bolts on cover look original (outer 4 without phillips and others with. All 10mm/M6 ?
Is bolts holding cams single-use? I can pull those from spare engine. What heli-coil kit would you recommend?

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Last edit: by katit.

Katit's 1978 KZ650 project 30 Dec 2020 21:44 #840894

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That's ugly. But my first question is what's up with that machined cam cap (I think right outside on the intake, number 8?).

I thought they were all supposed to be cast aluminum with the position number on top. That one looks like it's machined from steel? The caps are matched to the specific head and position. You can't swap them around or between heads. It would take a lot of work to make an accurate replacement.
'78 Z1-R in blue, '78 Z1-R in black, '78 Z1-R in pieces
'95 GPZ1100 (sold) , '00 ZRX1100
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Katit's 1978 KZ650 project 30 Dec 2020 21:47 #840895

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I noticed that too but it looks pretty legit and others numbered correctly... will open up spare engine I got and see..

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Katit's 1978 KZ650 project 31 Dec 2020 05:18 #840900

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Bad luck with that head. Looks like a bunch of stripped threads for the cam cap bolts and as mentioned, something wrong with that one cap. I think the proper screws have a 9 mark on the head and raised edges along the edges. Does your parts bike have a decent head on it?

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Katit's 1978 KZ650 project 31 Dec 2020 06:05 #840902

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Bad luck with that head. Looks like a bunch of stripped threads for the cam cap bolts and as mentioned, something wrong with that one cap. I think the proper screws have a 9 mark on the head and raised edges along the edges. Does your parts bike have a decent head on it?


Pulled cover from spare motor. Cover was painted. But gasket was there, no silicone. And all bolts seem to be in places. And #8 also.

Picture of # removed attached. Looks like brass with guides, pretty good work but uneven wear.

Cams on spare engine have more visual wear and surface rust on tips

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Katit's 1978 KZ650 project 31 Dec 2020 07:57 #840909

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Someone went to the trouble of machining a brass cam cap??!! Unbelievable... There are some really bad hack mechanics out there. Best of luck with your project. It sounds like you know how things should be done. With the advice and help from the guys on this board you should be able to straighten that mess out.
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Katit's 1978 KZ650 project 31 Dec 2020 08:04 #840911

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Is it brass, or badly overheated steel? A magnet will tell.
That head can be saved, but the time and expense would be unreasonable. Buying a parts bike may have been a brilliant move for this “restoration.”
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Katit's 1978 KZ650 project 31 Dec 2020 08:19 #840912

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Let me ask you this. Do they machine(bore) those caps together with head at a factory? I assume so. In that case - current head is no go.
It does look like brass, didn't take magnet but not overheated.

Vaguely remembering owner saying "something with clutch, may need to adjust cable". Not that I remember this and seeing what I am seeing it's probably waste of time to try to make it run as is. Need to pull engine and go through. I have spare one so between 2 and some money I am just going to rebuild and be done with it.

Pulling head I will want to check valves. "While there" - will want to check pistons/cylinders. And it's just so much time that I'd rather just clean/reseal and inspect whole thing. Motor doesn't look too complex.

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Katit's 1978 KZ650 project 31 Dec 2020 08:25 #840914

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Yes, the cam caps are align bored, which is why they are numbered and have directional arrows. It is possible to find a cap from another engine that is close enough, but with all the other problems, I think that would be an unwise choice.
You are right to suspect that the clutch will be worse than the po suggested.
1982 KZ1000 LTD parts donor
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2000 ZRX1100 not ridden enough

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Katit's 1978 KZ650 project 31 Dec 2020 08:29 #840915

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Oh well. OK. This is what I wanted so I got it B)

Side question - what size glass bead media to use in sandblast cabinet for engine casings? And where do you get them?

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Katit's 1978 KZ650 project 31 Dec 2020 08:43 #840917

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It is possible to find a cap from another engine that is close enough, but with all the other problems, I think that would be an unwise choice.


Also, the KZ650 doesn't use any bearing shells or inserts. The cam bearing surface is the machined aluminum of the head and cap. So if it's not a good match, you might find that your replacement cap has ruined the bearing surface on the head and ruined the whole head.
'78 Z1-R in blue, '78 Z1-R in black, '78 Z1-R in pieces
'95 GPZ1100 (sold) , '00 ZRX1100

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Katit's 1978 KZ650 project 31 Dec 2020 08:50 #840918

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So if it's not a good match, you might find that your replacement cap has ruined the bearing surface on the head and ruined the whole head.


"Good match" is a very tough call, not worth dealing with it. Hence no go with original head.
Curious what happened there but I guess we will never know

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