1980 KZ650F Cleanup and tune

As long as you have the petcock apart, it would be a good idea to polish the face of the lever control that presses against the smiley face oring. That surface should be flat, smooth as glass, and free of pits. The seat for the little oring that controls fuel flow should also be smooth and polished. Attention to these two details will help insure smmoth operation and good seals.

baldy110 wrote: Teflon tape works great for those Tees and lasts a long time. People don't realize JB weld epoxy breaks down in contact with gasolo that's why it came apart so easily.

I bought some today, and it will work nicely as a temporary solution

Other things will have to get taken care of first... I checked the compression and got really low numbers (30-50 psi). Oil on top of the cylinders did not improve much, 60ish on two but the other two were still low. I will finish checking the valve clearances tomorrow but I am a bit discouraged.

I do have another engine which I will also look at tomorrow. If it does better with a compression test I may end up switching engines until I can get the original one rebuilt. I am trying to not buy a whole gasket set and set of rings right now.

TexasKZ wrote: As long as you have the petcock apart, it would be a good idea to polish the face of the lever control that presses against the smiley face oring. That surface should be flat, smooth as glass, and free of pits. The seat for the little oring that controls fuel flow should also be smooth and polished. Attention to these two details will help insure smmoth operation and good seals.

I actually did that already. I lapped all the mating surfaces on a diamond plate. The factory castings are definitely not flat, but it's looking good now. I am a bit irritated that I evidently forgot to order the petcock kit, but now I have other things to keep me busy (namely compression). Thanks for the suggestion!

Engine on the parts bike is not good. Probably scrap (two cylinders rusty, all kinds of corrosion under the ignition cover and the engine doesn't rotate).

I finished measuring valve clearances. I hope I am doing this right. The manual says to do it a certain way (measure 1 and 4, or 2 and 3) but it's a bit confusing.

I'll try and explain it the way I understand, and hopefully one of you more knowledgeable fellows can tell me if I am doing it right or wrong.

After getting all crouched over to see the timing marks, I thought to myself... I need to measure the clearance when the cam lobe is not pressing the valve. So what I did was look at the camshaft and watch a lobe engage a valve, then after it lets off the valve completely I measure the clearance.

This is what I got:
Intake:
1) <0.03mm
2) <0.03mm
3) <0.03mm
4) <0.03mm

The smallest feeler gauge I have is 0.0015" so I don't actually know what the exact clearance is, but I do know that is way under spec.

Exhaust:
1) 0.13mm-0.15mm
2) 0.10mm-0.13mm
3) 0.10mm-0.13mm
4) 0.18mm-0.20mm (needs adjusted)

Does it sound right that all the intake valves are way under? That would mean they are not able to close all the way (correct??) which would explain the extremely low compression....

I think I am going to start tearing apart the other engine to see if there are any salvageable parts (like shims!) and the scrap stuff can be used for the wife's welded art projects haha

If your intake valve clearance is so low non of the valves can close completly (blow by gas) plus you could get some carbon build up on the valve seat surface and intake port. Lift the intake cam and put 0,10 mm thinner shims in. The exhaust valves don´t need to adjust.

jlaudiofan wrote: ....................... The manual says to do it a certain way (measure 1 and 4, or 2 and 3) but it's a bit confusing.

If it was my bike I would follow the instructions in the manual rather than making up my own procedure. After all, those instructions were written by experts who knew what they were doing, and they were written for use by professionals who have a vested interest in doing the task correctly. Ed

650ed wrote:

jlaudiofan wrote: ....................... The manual says to do it a certain way (measure 1 and 4, or 2 and 3) but it's a bit confusing.

If it was my bike I would follow the instructions in the manual rather than making up my own procedure. After all, those instructions were written by experts who knew what they were doing, and they were written for use by professionals who have a vested interest in doing the task correctly. Ed

The manual shows a cross section picture of the camshaft / valve, and it says to take the measurement with the lobe of the camshaft centered with the gasket surface pointing away from the valve, that's what I did for all of them. I will double check all the clearances though.

Checked the clearances again, same numbers. After measuring the existing shims, I need a 2 x 2.40mm, 1 2.30mm and 1 2.20mm shims.

I pulled all the shims out of the parts bike motor but none of them will work for what I need (too thick). I will order one of the HotCams shim kits from Amazon.
Also going the order the fuel petcock rebuild kit (which I forgot to order) and go ahead and get a gasket set too (and oil seals). It'd be silly to do all this work only to leak oil from all over the place :laugh:

That'll also let me pull the head and clean the combustion chambers and remove / clean / measure / lap the valves and put on a new head gasket.

Is there anything else I should check while I am digging around inside the engine? pull pistons and check bores, con ron bearing surfaces, measure rings?

Got the shim kit and finally had a chance to do some adjustments on valve clearances. 3 cylinders had improved compression (around 90) but one still has zero compression. That particular cylinder has a much thicker shim than the others.

I was hoping that valve clearance adjustment would get me compression, but I have a feeling it was run with such low clearance that the intake valves are pretty carbon crusted. I will pull the head, clean the valves, replace the valve seals, check the seats, inspect the valves, lap them too. I guess that's what rebuilding a head entails yeah?

Wondering if there is anything else to be done while rebuilding the head. I will most likely strip it and soda blast it clean before doing anything else.