Dang! Still having idle problems...help!

Bike is a '80 kz1000e. To recap, I just recently got the bike running. So far I have

1. rebuilt/cleaned carbs using K&L rebuild kits. I had to use the original mains since the kits didn't come with 110s. Left the accelerator pump disconnected while I wait for a new diaphragm.
2. set float heights
3. bench synchronized
4. ridden 500 miles

I haven't been able to get it idling well enough to do a real synchronization or to adjust the air screws, which are all currently set at 1-1/2 turns. The bike runs great under every condition EXCEPT idle and very small throttle openings. It hauls butt otherwise, pulling strongly above 2K rpm.

At idle it seems to be running on three cylinders. Number 4 looks like the culprit, since pulling that plug cap has very little effect, if any, on idle quality, if you can call it that. Also, I'm getting a fairly regular Poof! from the right exhaust. The poofs made me think that perhaps I wasn't getting consistent spark, but I put an inductive timing light on the #4 wire and it appears to be firing as it should.

So that would seem to call into question my carb rebuilding skills. Surprise! Can anyone offer any specific suggestions of things to try/look for before I go blindly tearing into the carbs for the umpteenth time? Maybe since it's #4 I can do what need to be done with the carbs on the bike?

rckz wrote:

Bike is a '80 kz1000e. To recap, I just recently got the bike running. So far I have

1. rebuilt/cleaned carbs using K&L rebuild kits. I had to use the original mains since the kits didn't come with 110s. Left the accelerator pump disconnected while I wait for a new diaphragm.
2. set float heights
3. bench synchronized
4. ridden 500 miles

I haven't been able to get it idling well enough to do a real synchronization or to adjust the air screws, which are all currently set at 1-1/2 turns. The bike runs great under every condition EXCEPT idle and very small throttle openings. It hauls butt otherwise, pulling strongly above 2K rpm.

I don't have one on my carbs, but the way I've been made to understand the accelerator pump function is that it provides more fuel at idle/just above idle to help compensate for the "clean air" crap that Kawi had to install to comply with Gov regulations.
So being that you state yours is "disconnected", that would be my first guess of the cause of your bikes idling issues.

Hopefully someone more familiar and knowledgable with accelerator pumps can confirm this, or correct me if I'm mistaken.

RetroRiceRocketRider wrote:

I don't have one on my carbs, but the way I've been made to understand the accelerator pump function is that it provides more fuel at idle/just above idle to help compensate for the "clean air" crap that Kawi had to install to comply with Gov regulations.
So being that you state yours is "disconnected", that would be my first guess of the cause of your bikes idling issues.

Hopefully someone more familiar and knowledgable with accelerator pumps can confirm this, or correct me if I'm mistaken.

Actually, the accelerator pump doesn't do anything at idle. When you grab lots of throttle, the pump will inject a bit of extra fuel to reduce/eliminate hesitation due to the relatively lean jetting of the bike. So no, I'm pretty certain it's not the pump.

Edit: Sorry if that sounded curt. I appreciate the suggestion. Thanks.

Post edited by: rckz, at: 2007/09/22 15:28

Carbs may be okay.

If not already done, would begin by assuring all non-carb components are up to specs:
Ample clean fresh well-filtered fuel supply;
Compression readings;
Valve clearances;
Ignition system (coils, plug wires and caps, new plugs);
Battery and charging system;
Chassis wiring (ground, connectors, voltage to coils).

Off idle performance would suggest most of the non-carb specs are probably okay. But because proper carb function requires proper fuel supply, good compression and adequate properly timed spark, the carbs should be addressed last, IMO.

Good Luck!

Have you checked to see if your carb holders are letting air leak in? Try spraying carb cleaner around the holders at low idle to see if engine dies. If the holders are leaking, they will suck in the carb cleaner and stall the engine or make it run erratically. Ed

Patton wrote:

Carbs may be okay.

If not already done, would begin by assuring all non-carb components are up to specs:
Ample clean fresh well-filtered fuel supply;
Compression readings;
Valve clearances;
Ignition system (coils, plug wires and caps, new plugs);
Battery and charging system;
Chassis wiring (ground, connectors, voltage to coils).

Off idle performance would suggest most of the non-carb specs are probably okay. But because proper carb function requires proper fuel supply, good compression and adequate properly timed spark, the carbs should be addressed last, IMO.

Good Luck!

Thanks. I forgot to mention is has a new air filter, and air box boots, and the valve clearances are all within spec, though one exhaust valve is borderline tight.

650ed wrote:

Have you checked to see if your carb holders are letting air leak in? Try spraying carb cleaner around the holders at low idle to see if engine dies. If the holders are leaking, they will suck in the carb cleaner and stall the engine or make it run erratically. Ed

Good suggestion. I'll try it.

rckz wrote:

...have...set float heights...running on three cylinders. Number 4 looks like the culprit...fairly regular Poof! from the right exhaust...Maybe since it's #4 I can do what need to be done with the carbs on the bike?

Hope not relying on the upside down bench measuring method to set float height as that is ball park at best. If not already done, would perform the "clear plastic tube test" to check the true service float bowl fuel level. And thereby assure the fuel level is not too high (which causes excessively rich mixture).

If had to guess, would suspect the pilot circuit is not yet cleaned to as-new condition. If the pilot adjusting screws are having little or no effect, it suggests trouble in the pilot circuit (where other components are up to specs).

Gotta love those new soft pliable air box boots!

Post edited by: Patton, at: 2007/09/22 17:19

Post edited by: Patton, at: 2007/09/22 17:21

Believe the below posted diagram shows your carb.

Here is a link that might be helpful.

pilot circuit

Patton wrote:

Believe the below posted diagram shows your carb.

Here is a link that might be helpful.

pilot circuit

Thanks for the info. I will check it out. I do suspect that my cleaning efforts were insufficient.

BTW, I used the plastic tube method for checking float levels. A messy job. Anyone have suggestions on a particular size/brand of tube to use? I got some vinyl stuff at the hardware store which sort of did the job, but what a pain!

Post edited by: rckz, at: 2007/09/24 00:30

for the clear plastic tube test, I've always used battery breather hoses(come with new batteries). nice and clear, about the right size and length, and they hold up to the gas as far as I know.

Either your cleaning efforts were insufficient or the float levels are grossly misadjusted. The accelerator pump doesn't have an effect on idle but once running, is necessary because it allows a clean idle to mid-range transition with stock jetting.