Outdoor Power Equipment and Small Engines - Kawasaki on push mower (Engine running problem)

Hello all, Great site here. I have a JD push mower circa 1990 with a Kawasaki engine 6 hp I think, it has a Mikuni carb on it. Self propelled 5 speed, blade clutch and all. I bought it brand new May 1990.
It starts OK, but when I engage the blade on high throttle it wants to die, if I move the throttle to low and engage the blade it will run and I can usually move the throttle to high and mow. But sometimes it will just sputter when I move it to high throttle. When it does allow me to move it up to high it will mow for a few minutes and then sputter. If I return it to low throttle it will stay running and let me return to high throttle for a while. I cleaned the carb really good. But I didn't soak it. The carb was replaced 5 years ago. It looks really good. It only has two screws, one for the idle stop adjustment and one more on top that you really can't get to when its installed on the mower. My fuel line is really soft, and I haven't checked to see if the gas cap is venting well yet, just read that on another thread. Put a new spark plug in today, it starts better, but still has this stalling problem. Is there a trick to the Mikuni carbs? It has a lot of hours on the mower, but it makes good power when its not stalling out. Sometimes I can choke the engine and engage the blade and it will let me move to high and mow for awhile. But then it will bog down and sputter again. Can I order a service manual for the Kawasaki or the Mikuni carb somewhere. Its a 14 year old mower, but its my first I ever bought and I have alot of senitmental attachment to it. I feel bad that its sick now. Thanks everyone Joe

Hello: Joe

Careful reading of the problem description reveals plenty of clues to base most likely causes of the conditions.

1)
Fuel flow to the carb is one. That has to be checked.
2)
The vent breather hole in the fuel cap is another. That has to be checked.
3)
Engine compression is another. Based on mower age, likely to be low. That has to be checked.

but when I engage the blade on high throttle it wants to die,
Fuel starvation likely. Check fuel flow to carb.

if I move the throttle to low and engage the blade it will run
Low fuel demand likely. Able to maintain speed based on limited fuel supplied.

and I can usually move the throttle to high and mow.
Based on fuel supplied before running short of fuel from the tank. Fuel in the lines to the carb, likely. Once depleted fuel demands are on the supply.

But sometimes it will just sputter when I move it to high throttle.
Same reason as above. Fuel supply likely.

If I return it to low throttle it will stay running and let me return to high throttle for a while.
Again, likely to be fuel supply. Check without the fuel cap on the tank. May be a restricted vent in the cap or in the fuel supply line (system) to the carb.
May also be the carb condition, which has not changed do to a lack of complete disassembly during cleaning. Fuel passages still restricted.

There is no "trick" to "Mikuni" carbs than does not apply to all diaphram carbs. All carbs have to accurately and constantly meter fuel. All carbs require a constant and full rate of fuel supplied to them. Which varys constantly based upon engine loads and demands.

Based on your well described engine symptoms, 3 primary factors to consider.
1)
Fuel supply to carb from tank.
2)
Carb condition. May still have internal fuel passage restrictions.
3)
Engine compression.
Starting "okay" as mentioned, is not a good indicator of engine condition. Compression is. Taken when engine is cold and again when warmed up to operating temp.

Compression testing:
Throttle fully opened both times.
Only one hit >compression stroke< determines accurate engine compression.

Most likely I haven't covered all of the possibilities. The other resident small engine service and repair professionals in the forum may be able to offer additional suggestions, advice & help.

Check back on your question several times over the next few days for additional replies.

Small engine repair parts, generic repair manuals and additional help are all available at all local small engine repair shops and or lawn mower repair shops in your area. Shops and dealers are listed in the phone book directory.

Regards & Good Luck. Sharp Advice.
Master Small Engine Tech. Web Site Host, Forums Monitor and Multiple Topics Moderator. "Accurate Power Equipment Company." Engine Diagnostics Services & Repair. Fast...Fair...Friendly & Highly Proficient Services....:D

I totaly agree with Sharp Advice. He covered what I would have. Do all of that and let us know how it goes. :)

Hello joeh20!

Another thing...you mentioned that the fuel line is really soft. I have seen hoses get so soft that they collapse internally and restrict fuel flow to the carb. If it hasn't been replaced in 14 years it probably needs a new hose anyway, and it's cheap.

Update. Today I replaced the fuel line and inline filter. I checked the gas cap. It had some mesh below the rubber part. But it looked good. I blowed air through it, it's clear. I mowed about 45 minutes with it and it's somewhat better. It sputtered about 3 or 4 times. But all in all maybe the old soft fuel line was part of the problem. Im going to go ahead and soak the carburetor real good, in that stuff they said on another thread, that comes in the can with that little basket. I had some stuff like that once before I think. That should help and can't hurt. I think now that the blade clutch needs adjusting also. If I engaged the clutch with a sharp motion it didn't bog down much, but if I engaged it too slowly it would try to kill the engine.
I guess the compression could be fading some, it is 14 years old. I'll try to get that checked also. For now I'm able to use it, just would like it to be it's old self again. Thanks again, it's getting better day by day.

If the "stuff" you're refering to in another thread is what I always recommend - NAPA #6401 Carburetor Cleaner - then use caution when using. This is strong stuff, use protective gloves and eyewear. Also make note that this product will destroy all rubber and most plastic parts in/on the carburetor...Remove any of these items from the carburetor before soaking. Let us know how you make out after the bathing.

Did you get it fixed? :)

Another item came to mind which I haven't come across in a couple years but...Kawasaki has a component to their ignition called an igniter module. I have seen many break down on higher rpm's, whereas the ignition was insufficient at top end but fine at lower rpm's. This module mounts to the speed control bracket (just to the right of the carburetor) and is about 1/2" square by about 1/4" thick, gold in color, with a single wire going to it. Just something to consider. You may want to check with your local Deere dealer about this.

I wondered about the ignition. It is still somewhat troublesome to run. It is starting better. Yet Wednesday while mowing it was still sputtering some when placed on high. I have seen that module, but didn't know it's function. I have about went to the end of my expertise with this mower. But I am learning so much trying to track things down. And you guys have been lifesavers through it all. My wife said the other day just fix it, pay someone to fix it, or buy one, But fix it none the less. She doesn't understand the challenge and satisfaction of repairing ones own power equipment. It's not where your going thats important, its what you see on the way that makes the trip worthwhile. The saga continues, poor old joe, can he finnaly mow?

Ahh! you're so right about the satisfaction of repairing something yourself...seeing that you've accomplished a difficult feat. Some things, however, we must concede and let those with knowledge take care of.
Note that if you do indeed have suspected ignition trouble, and since this is multiple source ingition system, it may be best to take it to a Deere service center. They will have diagnostic and test equipment to eliminate one item over the other so that you don't end up buying and replacing something you don't need, because, like my shop and all others I'm sure, if you buy an electrical component, we will not take it back. For there is a chance you could fry it without knowing.

I've got a 1988 john deere rider model 165 hydro LT having the same problems. I'm about to rebuild the carb and would like to find another outlet for rebuild kits that is reasonably priced than the JD dealer. Can some one help me identify this carb that's on a kawasaki motor? There's no markings on the carb except the Mukini stamp.
Thanks!

I have a 98 JD with the 6hp Kawasaki. I am having the same trouble with the carb. It sputters and it will run for a little while with the throttle in the choke position.

Did you clean it?