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TOPIC: 78 kz650 timing and cam problems

78 kz650 timing and cam problems 9 years 11 months ago #165184

  • jordan172005
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I just recently swapped an engine from another kz650 onto my 78 kz650 and I'm having problems with the timing and cams. When I put it on the cams were not in time right so I adjusted them and put it back together. Now when I turn the engine over it's like the valves are sticking cause you'll turn it over and you can see the valve smack the cam hard when they return and can also hear it. It didn't do this before I took the cams off but it wasn't in time and wouldn't run. Can anyone help me with this problem? Thank you

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78 kz650 timing and cam problems 9 years 11 months ago #165234

  • KaZooCruiser
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. . . maybe you need to adjust out all the slack in the timing chain. . .

. . . or there is something wrong with the chain itself. . .

Added:

I just reread your post.

If the valves are jumping back into the head, they may be bent slightly. It wouldn't take much of a cam misadjustment, which you mentioned, to cause problems with an interference-type motor

Post edited by: KaZooCruiser, at: 2007/08/20 19:23

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78 kz650 timing and cam problems 9 years 11 months ago #165264

  • jordan172005
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you think it's bent valves? I mean it's all eight of them. I pulled the buckets out and put some oil in there and the buckets spin perfectly so I don't think they're sticking.

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78 kz650 timing and cam problems 9 years 11 months ago #165310

  • reborn650
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Since you said you had problems with cam timing I would start there instead of yanking the head in search of bent valves.

Here is what I would do....have done:)


Pull the valve cover off and re-check the cam timing.

Remove the point cover on the right side of the bike.

Set #1 cylinder at top dead center. Check that the timing marks are showing #1 at TDC.

Remove or completely loosen the cam chain adjuster.

Pull off the idler gear on the top of the cylinder head.

Remove the cam cap bearings to get at the camshafts.

Line up the exhaust cam arrow on the front flat area of the cylinder head. Count 36 pins backwards towards the intake cam starting from the pin above the arrow on the exhaust cam. The 36th pin on the camchain should line up with the arrow on the intake cam.

Make sure the cam chain is on the bottom spocket on the crankshaft.

Re-install the idler gear and re-install the cam chain adjuster taking up the excess slack.

Using a 17mm wrench, turn the engine over by hand. Do not use the electric starter.

By using the wrench you will feel if the engine is turning over freely. If there is any contact with valves to pistons you will feel it when using the wrench.

If you have done the cam timing properly and are feeling contact between pistons and valves, then you will have to remove the head and disassemble the valvetrain to inspect each valve stem for straightness and valve face for sealing.

I think it is unlikely that you bent all of the valves at the same time unless the timing of the cams were out 180 degrees and if you really cranked on the starter for an extended period. Worse case scenario is that you bent one or two valves.

My last bit of advice is to get a manual cam chain tensioner from APE. The design is bulletproof and foolproof in the set it and forget it category.

Just my two cents here from experience:)

Cheers-Colin Firth-Ontario Canada

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-1977 Kz650 Custom bought new by brother. Now with 810 kit, GPz750 cams, intake valves, Mikuni 29 smoothbores, velocity stacks, Dyna Igntion, MAC pipe and other goodies.
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78 kz650 timing and cam problems 9 years 11 months ago #165339

  • BSKZ650
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if you think you bent the valves, pull the cams, use a compression guage with the schrader valve removed, hook the compressor to it and listen in the carb and exhuast for air, if you hear it its leaking and you prob bent some valves:S

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78 kz650 timing and cam problems 9 years 11 months ago #165374

  • KaZooCruiser
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jordan172005 wrote:

. . . When I put it on the cams were not in time right so I adjusted them and put it back together. Now when I turn the engine over it's like the valves are sticking cause you'll turn it over and you can see the valve smack the cam hard when they return and can also hear it. It didn't do this before I took the cams off but it wasn't in time and wouldn't run.


Hi Jordan172005. . .

It didn't do this before, and after you "adjusted them and put it back together. . ." you now have sticking valves.

I don't know how you turned the engine over once you had it back together. If you whizzed the starter, and the valves were hanging down in the path of the piston, bang and bend is the result. The number of victims of that negligence is anyones guess.

It wasn't clear from your post that all eight valves were binding.

You might pull the buckets again, and push directly on the valve stems with a screwdriver, and see what kind of binding is occurring on the valve train that way.

It's hard to conceive of someone bending eight valves.

But it kind of reminds me of the time when I was fixing copiers for a living.

We had a new guy, who disappeared behind a unit with a hammer one day. I asked him what he was planning to do.

He told me that the paper pick up shaft was stuck and wouldn't come out.

Turns out he had overlooked the securing e-clip which held the shaft in against the retaining bushing. Pull the clip, pull the bushing, and the shaft drops out.

No telling how much damage his ignorance would have caused to a helpless copier otherwise.

Hope you get it figured out.

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78 kz650 timing and cam problems 9 years 11 months ago #165427

  • RonKZ650
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Sounds like the cam timing is still off and valves are butting together. If so they are bent. You can tell by checking valve clearance. If you have gobs of valve clearance, the valves are bent. If you're sitting pretty much in range of .5-.20mm chances are valves are not bent, but I'd still bet the cams are timed wrong. You must have the center sprocket that goes between your cams in place before you turn the engine over as well as the main tensioner behind the cylinder.

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