1981 KZ750 E2 will not accelerate past 70 mph

"Whacking valves" (technical term) is an old remedy for sticking valves aka a "technical tap"

(j) If leakage is still occurring after a
recheck, it may be possible to correct a low
reading. This is accomplished by placing a fiber
drift on the rocker arm directly over the
valve stem and tapping the drift several times
with a hammer to dislodge any foreign material
between the valve face and seat.
NOTE: When correcting a low reading
in this manner, rotate the propeller
so the piston will not be at TDC.
This is necessary to prevent the valve
from striking the top of the piston in
some engines. Rotate the engine before
rechecking compression to reseat
the valves in the normal manner.

Installed new shim on the #2 cylinder exhaust side. Went from a 260 to a 245, .006" thinner.
This resulted in a.005" clearance, prior to repair there was no clearance at all. Started bike, rode it short distance to warm it up. Performed another compression check, still only have 90 psi on #2 cylinder. The other cylinders still had about 125/130 indicated. That was enough for me. The head and cylinder block have now been removed. The valves will at least be lapped, re-ground if I can not get a good seal. The rings will be replaced. Cylinders will be measured, re-worked only if required. This has now become an off season project. I do not anticipate having these repairs done before next riding season. Thanks to everyone who offered advice on this problem I have been having.

For now I will contine to ride my other Kawasaki, a Concours 1000. The heat has finally broken and now I can look forward to the best months for riding in Minnesota, September and October.

I did get some good news last week, no cancer found on my follow up check. I have made it 18 months since I was diagnosed with cancer. Last year was several surgeries and months of chemo.
God has been good to me.

I will update this site as I progress on my project.

Glad to hear about your continued good health SoDak52. I imagine it makes all other life's little challenges seem much less important in comparison. Hope you will be starting a new build thread on your repair. Look forward to seeing it because I am in at the verge of starting a similar repair on mine due to a broken front cam chain guide. Figured I may as well check all specks, lap the valves, put new viton valve oil seals and new rings. And any cam chain system parts that may need replacement. Keep us posted.

Joe

Don't rely on seting up the timing by the marks on the sprockets, I found this to be wrong in the workshop manual. Use the degree's as listed with a timing disc bolted onto the pick-up centre bolt and using the thinest of feeler guages, I found my inlet cam was acually 1 tooth out and when set right, it red lined it for the first time since I bought it.

SoDak52... did you get your problem figured out?

I just did a total carb cleaning, replaced my fuel/vac lines from the petcock and found my ride was really flat @ anything over ~6k RPMs. After a closer inspection I found my fuel line had kink in it. You may want to look closer at your fuel and vaccum lines and see if you're having any issues there.

Hey, so I don't know if you've found a solution, since this is a really old thread, but I was having the same issue on my '82 KZ750 CSR twin, and after trying everything including new coil, cleaning carbs, new hose etc, I found that the air suction reed valves that are on the top of the cylinder head cover were installed upside down by whoever owned the bike before me, so it was letting exhaust into the air intake and choking out the engine at high RPM, also it was causing it to idle rough too. I'd take a look at them and make sure that the side with the reed is facing down, not up, because there's nothing preventing you from putting them in upside down.

Adam