Not running smooth

I let my 1975 Z1B 900 sit for a few years; divorce, move, Iraq tour, and now I've gotten it running again. It runs well at high RPM, but mid and low RPM not so much.

The exhaust "burbles", and will pop when decelerating. Idle is erratic. Kind of weak pulling away from the curb, and rough acceleration until it hits aroungd 5K, and then it runs great. Ran great when parked it few years ago.

Cleaned carbs twice, cleaner and air through all orifaces. Cleaned tank, fuel cap, and petcock. New fuel line and filters. New plugs, gapped at .030. New air cleaner. New rubber plug thingys on the bottom of the carb where the vacuum gauge hooks up.

Cylinders 1,2 and 4 are about 400 Deg F after running, # 3 is about 300 deg. 1 and 2 plugs look good, 3 and 4 plugs are dry and sooty. The picture (if it comes through) shows 2 3 in that order.

Tried screwing down the pilot screw on 3 and 4, no effect. All are about 1 1/4 turns out.

Did you change the oil ? Sounds like spark plugs 3 & 4 are already JUNK.

I would have normally replace the pilot jets, instead of trying to clean them.

Look at your float height on 3 & 4. The top of the floats should be even with the top of the pilot jet casting (lower would be rich)

Normally I would run pilot screws at 2 1/2 turns out, but never richer than that. That setting works for all Kawasakis

It's good maintence to pull off the intake manifolds, if you have the carbs off. 3Bond 1107B is a fantastic sealer for that, but it is only avaliable from Suzuki.


Carb sync May be a problem too, 900's didn't have the best setup. With a sync guage lower the slides as much as possible to raise the manifold vacuum, adjust idle as necessary. Then sync the carbs from that point.

I wouldn't recomend doing the carb sync, unless you have done the above first. Clean oil and new spark plugs always. (New spark plugs can be JUNK in 5 minutes of runtime, when there is gasoline in the oil, or with ignition and carburation problems)

Thanks. Yes, I did change the oil.

I bench synced the carbs with the piece of wire. I'll see if I can order new pilot jets, and will check float levels.

Don't have a sync gauge. Local bike shop refuses to work on bikes as old as mine.

I'll also get some new plugs. I'm running B8ES.

Thanks again; I'll check back in as I get this stuff done.

Maybe we can make a pair with some plastic tubing and some anti-freeze/coolant.

I need to make one for a Banshee next weekend, I'll see if I can't expand it into a 4 cylinder sync guage.

Or 4 vacuum guages with a needle valve or a inline restrictor with aprox. a .020" to .030" hole, that controls the vacuum to each guage, is another way to make one.

I have had this problem before with mine, and a friend of mine did too.
The problem with mine and his was the intake boots were leaking. I tried to seal them with gasket maker and also wrapped the boots with electrical tape that helped out a lot. But still had a problem with idle and curb take offs. It wasnt till I purchased new boots then the problem went away. I can have it idle at a stop as long as I want now with no pop or burbling.
The other guy had one enrichening valve leaking on him. We solved that with vacume caps (the thick black rubber kind) and cut the heads of the caps off poked a hole in the end for the guide on the enrichening valve to patrude though and stuffed the ends of the cap in the vave resess. It worked great;) The vaves at the dealer are $25 each (4 is needed) we fixed it for $.99B)

As for syncing the carbs I just used a drill bit for measurment under the slides. Ihave round slide manual carbs.

Post edited by: Snakebyte, at: 2007/06/05 08:54

Drill bit is a good idea.

I'm not sure what an intake boot is? Is that the rubber intake manifold, aka the airbox?