Vacuum leak?

It's throughout the power band. It's weak feeling and can't quite catch up with itself and I try to push through it but it just doesn't pull hard like it used to. It starts fine and fires up with the choke. When I let the choke off after a couple minutes I have to blip the throttle a little. Then it hangs a little and settles. It's not a smooth idle. I pulled the carbs again today and measured the float levels. With the manifold side on the bench I measured the point where the float tang touched the needle. 24mm on all. I don't think it's a float issue. The plugs are sooty. I'm gonna pull the valve cover again and check it and the specs again while waiting for parts. I'll get another round of new plugs on standby so I can install them after the manifolds get here next thursday from z1. I wish they had a preferred customer plan that rewarded you for all the cash you throw at him. Well... I do have the coolest bike on town!(When it's running right)

I been reading all your postings about your bike. I have been around that motor since it was brand new in Kawasaki dealerships. I used to keep notes on all my jetting projects on Z1's, Kz900's, and Kz1000's from all the way back in 1974 when I started in dealerships. The 1976 KZ900A4 had the richest stock jetting specs of all the big KZ's. You know for sure you have the stock carbs from that year on your bike? The correct carbs should have air screws back near the bellmouth of carbs. I hope someone before you did not stick you with some late '77or 78 KZ1000 carbs. Those carbs have the fuel/air screws underneath the carbs on the float bowl gaskit area. Those carbs are a nightmare to rejet. Are your individual filters clean? Does your motor have at least 120 pounds per hole? Does your Kerker have a EPA baffle, or the old style Comp baffle?

If you have good compression, a Kerker Copm baffle, clean K&N or Unifilter individual filters on true 1976 KZ900 carbs try running 117.5 or 120 REAL Mikuni brand main jets, and the air screws set about 3/4 turns out. This is the jetting specs I have in my book for your bike in Chicago altitude. Lean is mean!!! I never ran 125 mains in any stock Kz motor and carbs that I ever worked on. You should not have black sooty spark plugs if your jetting is close. I never ran anything but NGK B8ES spark plugs in my street Kz's. I used to get Champion plugs for free, but they never lasted more than a few miles in my motors till they started to misfire. Try it, you might like the way it runs.

Dr. Gamma sounds like he's on to it -- running too rich. That would explain the plugs condition.

If you measure the front mouth of the carb, does it read 26mm and change, or 28mm and change?

The stock Kz900 in 1976 dropped down from the 28mm used on the 73-75 Z1-900 down to 26mm and Kaw kept the 26mm carbs for the 1976 and '77 Kz900, and the 1977 and 78 Kz1000, except on the 1978 Kz1000-D, the Z1R, they went to 28mm for those.


Another thing about chasing intake problems. I ran into this with a Gs1100 a few years back. The bike was running really lean, the plugs were clean as hell, every bit of fuel that got into the combustion chamber got totally burned and the plugs had no desirable 'golden brown' look, they were whitish. So I knew the bike was running lean.

I pulled off the rubber intake boots and found cracks inside -- BIG cracks, "ah-HAH there's the problem" nope, I shotgunned that to the tune of $75 and the new intake manifolds changed nothing.

Since I had the carbs off anyway I pulled and looked at all the jets and soaked the carb bodies in Berryman's overnight.

The main jets had the stock jetting number engraved, and the bike had individual pod filters and a race-style 4-into-1, "ah-HAH!" I thought, that's why it's lean, he forgot to jet up." I shotgunned that and went up a few sizes on mains. Still ran lean as before.

Then I noticed the stock main jets had a LARGER HOLE than the bigger jets I bought -- so that told me the prior owner had also been chasing the lean-running condition and DRILLED OUT HIS MAIN JETS (not cool at all).

So never trust the engravings, compare the jet size with a known-good main jet before you decide.

You sound like you have a depth of experience and may know all this already, but if the plugs look like that, it's not running lean. May be choking on too much fuel or insufficient ignition.

Have you verified that when you rev the motor that your battery reads 13.5vdc or higher? Signs that your charging circuit is okay. You have new coils and wires and new ignition it sounds like -- so overly-rich jetting, and/or weak battery causing ignition problems.

In steady-state, with the battery disconnected from the harness, a good battery will read 12.55 to 12.65 volts, because each cell puts out 2.1vdc.

You might check your battery, takes 5 minutes.

And to know if any of your changes are affecting the bike, I would clean or put new spark plugs in after a major change, like new intake boots, or new jets. Once plugs are all black and sooty it is hard to use them as a clue for how the engine is running.

Hey newOld_kz1000 you would not believe how big of a main jet size some of our customers asked for their KZ's. Back in Chicago in the 70's you had to have a "9" or a Grand" with a Kerker, and some "SMOOTHBORES" They would ask for some 135 or 137.5 jets because their bike don't run right, it still "cuts out".

Sounds like Mr. Matteson needs new intake ducts, and to lean that sucker out a bit. I forgot about people drilling out main jets!!! Glad you brought that up!!! Should have told him to check the timimg at the full advance mark too. I would rather have the timimg off a bit at the "F" mark than at the advance mark myself. Once a plug is black, its time to replace them. Everytime I change main jet size, I put new plugs in. You can't read a used plug. Once I get close with the jetting, its time for a plug chop. Run that motor at max rpm in top gear, and when you hit redline hit the kill switch, and pull the clutch lever in at the same time. Coast to a stop, and pull the plugs and see what you got. As long as the ground strap is a little brown, you are there!!!!

Dr. Gamma wrote: Hey newOld_kz1000 you would not believe how big of a main jet size some of our customers asked for their KZ's. Back in Chicago in the 70's you had to have a "9" or a Grand" with a Kerker, and some "SMOOTHBORES" They would ask for some 135 or 137.5 jets because their bike don't run right, it still "cuts out".

Sounds like Mr. Matteson needs new intake ducts, and to lean that sucker out a bit. I forgot about people drilling out main jets!!! Glad you brought that up!!! Should have told him to check the timimg at the full advance mark too. I would rather have the timimg off a bit at the "F" mark than at the advance mark myself. Once a plug is black, its time to replace them. Everytime I change main jet size, I put new plugs in. You can't read a used plug. Once I get close with the jetting, its time for a plug chop. Run that motor at max rpm in top gear, and when you hit redline hit the kill switch, and pull the clutch lever in at the same time. Coast to a stop, and pull the plugs and see what you got. As long as the ground strap is a little brown, you are there!!!!

I could not help but notice that you possess an RG500 Gamma, I rode one back in '86 and it was for sale but was told the cops would seize them if they caught you, good on you there, that RG500 was a monstrously fun accelerating trip. I ended up buying a new '86 gsxr750 instead.

I have a 1985 RZ500 Yam V4 2-stroke being shipped from the East Coast on an Allied Motorcycle Transport truck due to arrive here in a week, can't wait to tear into that project.

Drilling the jets is a disservice to the time commitment of all the people who will work on the carbs after you if you don't give them a heads up about it. I would not have minded it if the seller had *told* me and I didn't have to find out the hard way on the ol' Gs1100 there.

I have over-jetted more than one bike and if the '76 Kz900 he has now has those symptoms, should be easy to set right.

Matteson wrote: ...pulled the carbs again today and measured the float levels. With the manifold side on the bench I measured the point where the float tang touched the needle. 24mm on all. I don't think it's a float issue. The plugs are sooty....

Has the clear tube test been performed to determine whether fuel levels are within specs?

Good Fortune!

I have stock 26mm carbs. Genuine Mikuni 125 jets. Yes, they are bigger than the 115's in size upon visual inspection. I understood the 115's were rich from the factory. No baffle. Clean air breathers. Clear tube method was performed before with good results. Timing is at set at the F mark. I will borrow the timing light again and set it to full advance. Upon the advice from the Doc I'll try the 120's. Battery is sound. I'll go buy new plugs should I gap them a little larger?
When running a Suzuki or Kawasaki with a Dyna-S and high performance coils set plug gap at .026? I read that on kz900.com True? Thanks guys

"""I could not help but notice that you possess an RG500 Gamma, I rode one back in '86 and it was for sale but was told the cops would seize them if they caught you, good on you there, that RG500 was a monstrously fun accelerating trip. I ended up buying a new '86 gsxr750 instead.

I have a 1985 RZ500 Yam V4 2-stroke being shipped from the East Coast on an Allied Motorcycle Transport truck due to arrive here in a week, can't wait to tear into that project.""" From newOld_kz1000



I come from the Land Of Lincoln where anything can be had for a price. Judges, presidential elections, and a title for a Gamma!!! A "small" contribution for someone running for Governor in Illinois will get you a title for your Gamma!!! I think like 5 out of the last 6 Governors of Illimois are in prison, or have served time. Like they say in Crook County, vote early, and vote often!!!




I hope its legal to post a photo of a non-Kawasaki bike. Or should I say how much will it cost me to post a picture of a non-Kawasaki motorcycle??

Nice RG, I can't help but notice the large cast aluminum frame section at the gooseneck, the whole 500 Gamma frame must have been aluminum like the GSXRs which was pretty exotic in 1986.

My Rz500 has the steel frame, only the Japan-market RZ500s had aluminum frames, dang it.
Incredible.

Nice LTD GSXR in the background there, hold on to that one, it's worth more ultimately than most baby boomers have saved for retirement!

Thanks. You can definitely tell the RG500 and the first GSXR's were designed at the same time when you park both side by side. The frame tubing are identical on both bikes.

No, my Limited is not stock anymore. The big buck Limiteds are the ones that somebody kept all stock. I cut on the fairing so all the Yoshimura goodies would fit. And I threw away that stupid looking rear fender, and plate lamp. Plus this and that was added. Just can't see keeping ANY sportbike stock for more than a week in my book.

Issue on the KZ 659's is battery voltage at the coils
as the harness gets old the voltage drop's and cause's issue's like your having.

Easy fix is to use the factory coil wire to trigger a relay and
run a new coil feed wire.

I had the coil mod on the bike and got rid of it because I am getting the same battery voltage at the coils after a little cleaning. I have a bare bones wiring on the bike. I'm gonna get new plugs tonight and try this again.