1982 KZ440 LTD - Sputtering and High Idle

Hi Everyone! I'm the proud new owner of a lightly custom KZ440 LTD. I purchased it not running this summer, and went through the carb meticulously, while replacing all the O-rings, pilot screws, and float bowl gaskets. I adjusted the pilot screw as per the factory service manual. Following that, I changed out the plugs, put in some fresh gas, and it fired right up!

The idle seemed a little high, around 2500, and the idle adjuster won't bring it down. Despite that, I rode about 4 hours with it yesterday , and it ran like a charm. No sputtering or hesitation, and it wound right up to 135km/h without issue.

So.... I started it up today, and it is sputtering and hesitating big time under load. Light acceleration is OK, but anything more and it sputters hard. I have the stock airbox in place, seated tightly.

Any thoughts on troubleshooting this issue? I haven't checked the plugs today, but was thinking I might try some iridium ones

Thanks in advance for any insight!

Iridium spark plugs are a waste of money. I'm unaware of any iridium plugs that are a proper match to your bike anyway since they all have a built in resistor and your bike calls for non resistor plugs. I strongly suggest you buy a factory Kawasaki service manual instead and do some maintenance (valve adjustment, clean out the brake system, air filter, etc).

The high idle suggests a vacuum leak. Continuing to ride the bike this way will overheat the engine. Not good.

Hey thanks a lot for getting back to me!

A couple of things - my bike has a resistor plug in it now. The Canadian model takes BR7ES instead of B7ES for some reason.
I do have the factory service manual as it came with the bike. I used to to go through the carb. I have cleaned out the brake system and air filter, but haven't done the valves yet. I have never done valves, but my understanding from reading other threads is that it's a fairly simple procedure with this model. I will refer to the service manual for this, and to diagnose my vacuum leak. I haven't done that before either, but have read something about using an unlit propane torch.

The propane trick should help you find the leak. It'll most likely be around the carb boots if there's a leak, which would be my guess.

OK - I'll give it a go after work tonight and report back. Thanks again

Hey Guys,

So last night I sprayed carb cleaner all around carb and boots, but no change in idle whatsoever. There was a slight change when I sprayed towards the airbox side, but hardly. Nothing on the engine side,

Another thing to note, is that while the bike needs choke to start, it wants to die after about 15-20 seconds on choke without throttle input. after blipping the throttle for about a minute, I can take the choke off and the idle will hold. It will idle at 1100-1200 for about 3-4 mins, then the idle climbs slowly, settling at 2000-2500. This is with the idle screw on the lowest setting of course. Any application of choke during this period kills the engine.

Regarding the sputtering, it only happened that one time yesterday morning. I've had 3 separate rides since with no problems at all. The only difference is that one time I hadn't let the bike warm up as much.

Aside from valve clearance, which I will check over the weekend, any further thoughts?

Thanks again

A valve clearance check and adjustment is a requirement for a good carb adjustment and sync .
Clean tank, in tank fuel filter, float bowl high, ignition timing okay ?

What is a pilot screw?
Sounds like your idle circuit is partially plugged.
Clean your carbs and adjust your idle mixture screws.


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The tank and in-tank filter are clean. Haven't checked fuel level or timing, but I will add that to the list for the weekend!

I cleaned the carbs pretty thoroughly, Soaked all metal parts in carb cleaner for 2 weeks, replaced all O-rings, 'Pilot Screw' (as it's labeled in my service manual, see image and #42), it's O-ring, spring and washer, and cleaned all passages with a piece of wire brush. I suppose I could go through it again though. I'm going to check the float level, timing and valve clearance for sure this weekend. I put some seafoam in the fuel as well to help clear anything I may have missed.

Are we talking about the same thing when we say Pilot Screw vs Idle Mixture Screw?