TOPIC:

My son's 81 KZ1000 has these carbs installed. They are not the stock carbs and I don't think they are vm29. So how do I sync them? I have the gauges hooked up and I've synced dozens of CV carbs but these are throwing me for a loop. Note overall idle speed screw isn't even touching the stop and I have 3k rpm idle.

Here you can see what I thought were the idle speed sync screws. On the left with the slotted head and lock nut:

Now here is my problem. it doesn't seem like they act normal. I can screw the slotted head in and out 2 or 3 full turns and the sync gauges don't act like I would expect. Scre them in and the vacuum goes down a little then back up. Screw them out and vacuum goes down a little and back up. But now here is the confusing part when the vacuum goes down the engine speed up! In any event I can go back and forth and within a couple of seconds the engine slowly goes up to 3k rpm. It's like my adjustments do nothing. I still can't bring the idle down no matter what I try.

I just put new Z1 parts carb holders on it. But that $65 did nothing for me. Valves are all at .010 mm.

Early VM 28's. Bench set them with the idle stop screw at the center of the adjustment. Use a drill bit or thick wire as a gauge to make the slides all the same. Put them on the bike and sync them. There are two plates connecting 1/2, 3/4 together. They must be flat. They're to keep the slides moving together. They can be tricky.
Steve

Glad you said that. I was in the process of pulling them back off and checking bench sync. should have done that when I had them off the bike last time to replace the carb holders.

Steve, you are good! I bench synced them with the idle adjust about 1/2 up like you said. Sync gauges were so close I didn't mess with them. Did the idle mixture screws to idle max, touched up sync screws and the bike really smoothed out. One final adjustment on the overall idle and it purrs like a kitten at about 1100 rpm (indicated on the tach) but sounded more like 900 to 1000. Never trust the tach. Trust your ears.

Couple of notes.
One, the idle adjust screws work opposite of CV carbs. Screw them in to lower slides.
Second these adjustment screws are a lot more touchy than on a CV. A fraction of a turn makes a big difference in sync gauge reading.

Now rev the bike around 2500 RPM of where you can hear a miss then dial it out with the air bleed screws. I still have my 28's. Just wish I took better care of them.
Steve

We could not get it to stutter at any rpm up to about 6 or 7 k. Son test rode the bike and confirmed we still have a high rpm stutter but only under load. So I can't duplicate the problem while sitting still. I'm beginning to think it's coils or wires. Plugs are new. He changed plugs first thing then asked me to check out the bike when plugs didn't fix it. But another thing I don't remember is if the air gap on the igniters is adjustable? Carbs were pristine but I pulled all jets and emulsifiers and cleaned them anyway.

What mains are you running?
Steve

Honestly didn't note the size of the mains or pilots. My thinking was this thing has been running great for 5 years or so and this is a new problem so I disregarded jetting as an issue. That being said I cleaned the mains, emulsifiers and pilots anyway because why not? They were not dirty or clogged in the least. Also the nature of the problem was that it was running fine then the high idle and high speed stutter progressively got worse and worse over about 3 weeks time. Now the one problem I had with the idle adjust screw not touching the stop has been there for years but it wasn't really a problem. Just an annoyance. I decided to fix that part while I had the carbs off to replace the carb holders.

I'm still kinda leaning toward the high speed stutter under load as being related to the coils or wires. Those coils were off of a 82 CB900 that I had laying around. I put them on last year when the original, looked like OEM, coils failed. When I installed them it was supposed to be temporary to prove the coils were his original problem. But we never did buy new coils and wires. I guess I could swap the coils from my KZ1100 to see what happens. The problem with that is the primary hook up uses spade connectors on his KZ1000 and mine uses eye terminals. I'll have to make some adapters to try them.

Forgot to mention that coils on my 1100 are Dyna.

I know this is a little late for a reply but I have to tell what we found to be the high sped stutter. The wiring harness, which contains the power to the coils, had shifted position and was actually rubbing on the chain. Caught it before it cut the wire and had only rubbed the insulation off a very small spot. We taped up the bare spot and tied the harness up out of the way with tie wraps. Bike now runs as it should.

Thanks for the suggestions. I was convinced it was a coil problem and it turns it was a coil wire problem. Just glad my son found it before we pulled the coils off of my KZ1100Ltd. Easy simple and quick fix.... gotta love it.

Your going to have a hard time syncing those carbs with out the carb linkage washers. Your pictures show they are missing. These are huge in keeping carbs running together. I believe these are a large reason Mikuni changed the system in 76. I usually use 2 per side. You can get them at Z1 enterprises. If you ever want to trade those carbs off for a set of 34 CV that came on that bike let me know. I may even have an airbox to go with it.

Link plates will help for sure and also use vacuum gauges on the carbs with the gaskets and tops installed. Smoothbores are adjusted with the tops installed as well as apparently there is a chance for draw around the slides if not covered throwing off the accuracy of the adjustments.
Good luck.