TOPIC:

Noise just went away? What tensioner are you using? When you did the carbs, did you clean or replace the main jets?

Tensioner issue is resolved. It is the two wedge style without a set screw. I replaced the main jets.
122.5s are stock, which are now in it. I've tried 122.5, 127.5 and 132.5. I did find the carb intake vacuum ports had two loose caps on them which I suspected was allowing unmetered air to the intake. Aha! Or so I thought, no difference. Virtually every setup results in the bike losing power at just over 4K rpms. Which is the point when the mains are the only thing supplying fuel, correct? What I've done engine related:
Ultrasonic clean and rebuild kit on the carbs (K&L kits from Z1E) 37.5 pilots, 122.5 mains.
New Dyna coils with new Dyna plug wires and the Wired George mod applying battery voltage directly to the coils.
New BS8E spark plugs
New air filter
Valves all adjusted to cent of spec. Valves lapped. New valve stem seals.
New base, head, and cam cover cylinder gaskets installed.
Removed, cleaned, lubed ignition advance mechanism.
Cold air injection removed, APE covers installed.

This weekend I'll re-recheck the fuel level in the bowls. I'd love a few suggestions.

Did you replace the fuel valve? Check it for adequate fuel flow and vacuum at the diaphragm if OEM.

I replaced the petcock with a Pingel. Love them. Pablo on KZ650 suggests I take a long hard look at the sliders and diaphragms. Then look at the spark advance dynamically with a timing light. It will be Saturday before I get back to it.

I got a chance to get back out in the garage this evening. I did a carb swap with the bs34's off my 83 KZ1100 which are known to be a good set. I'll fire it up in the morning, do a test ride, then a dynamic timing test to see if and when the advance comes in. Note that is was removed and lube, reinstalled but need to see it in operation.

All carbs referenced are Mikuni BS34s. I swapped the carbs on from my 83 KZ1100 and it runs fantastic. Just did 120 miles on it. Wonderful machine. So I took a harder look at the original carbs. Two of the carb slides drop in a smooth pneumatic fashion when I raise them manually. Two of them drop rapidly with a slap when they land on the bottom. I removed the tops off of each carb very slowly/carefully. The rubber diaphragms were all seated properly. Top of the carbs appear perfectly flat as do the mating surfaces on the caps. I shined a bright light on the problem diaphragms while stretching them gently. No splits, ho holes.

I went back to the carbs from hell on the 85 GPz 750 Project. 3 out of 4 drop rapidly with a slap, only one drops relatively slowly.


Prior to installing the set off of my KZ1100, I raised each of the carbs sliders several times. All four drop smoothly and slower with a pleasant little woosh sound. So I believe I have my hands on the root cause of the problem. The big question is how do I address the slider issues? No binds in them, I lifted each one by the edges of the rubber diaphragm, turned them slowly, raised and lowered them several times, no binds. It isn't like that is a complex mechanism, so what does one do to fix them?

Try the thumb test by raising the slide then put your thumb over the large vent at the top then let the slide go down. It should go down slowly. If not there's a leak. Could also be the rubber is too stiff for them to move freely.
Steve

You are talking about the wide opening at the top of the airhorn, correct?

Yup.
Steve

Very good reply Steve. I didn't know what port to plug up to confirm the diaphragm holding vacuum.

Got back into the garage for a few minutes and I may well have run across the carb issue. First I put my thumb over the slider vent on the intake bell. 1,2,4 all barely moved. #3 slipped down slowly but significantly more quickly than the others. I started to take the top off the #3 carb and noticed the brass choke was backed out (unscrewed) about 3/8' spinning freely on the side of the carb. I tightened it up and now the slider behaves like the others.