Kawasaki engine issues

[Thumbcocker]

Our zero turn has a Kawasaki 24 hp engine. It is turning over slowly and will backfire sometimes. Replaced solenoid and battery. Charged battery fully. No change. Last week it started with the booster pack. Once started it ran beautifully. Did not start tonight with boost pack or battery charger in boost mode. Starter?

[Winger Ed.]

Starter?

That'd be my first guess.

The backfire might be from it turning over so slowly and not a engine problem.

I've had one or two on old cars that you could take them apart, clean everything real well,
if the brushes looked decent-- put them back together and they'd be OK.

[Gewehr-Guy]

Maybe a bad ground on the engine block?

[samari46]

Have you cleaned the battery terminals and lugs one the wires?. Had the same or almost the same with mu Kubota tractor. battery posts were black and some corrosion on one of the lugs. used the brush that can clean both the posts and the inside of the terminals or lugs. Started up but turned over slow. Put on 2amp charger overnight. hook the battery up and same thing. New battery time. Recleaned both new battery posts and lugs and started right up in 3 cranks. Old battery kaput. Check your switches as one could be on and you don't notice its on. On my Kubota the light switch is a multi function for headlamps, signal lights and flashers. When I put the new battery in service and sitting in the seat one position looked odd. Yep the 4 way flashers were on but no lights until engine is running. put the switch where it's supposed to be. Frank

[Petrol & Powder]

That engine has an automatic compression release mechanism that holds the exhaust valve slightly open at very low rpm's (like when first starting to rotate the crank). If that mechanism fails, the starter motor must overcome the full compression of the engine and it will not spin fast enough to start.

So if you eliminate all of electrical problems (battery, cables, starter motor, etc.) the next place to look for slow cranking is the automatic compression release.

[Lloyd Smale]

its possible to that because of the compression release they have it programed to advance timing to make it start easier. If the release isn't working it could have to much advance for the compression and actually be detonating (preignition or spark knock in other words)
That engine has an automatic compression release mechanism that holds the exhaust valve slightly open at very low rpm's (like when first starting to rotate the crank). If that mechanism fails, the starter motor must overcome the full compression of the engine and it will not spin fast enough to start.

So if you eliminate all of electrical problems (battery, cables, starter motor, etc.) the next place to look for slow cranking is the automatic compression release.

[trails4u]

its possible to that because of the compression release they have it programed to advance timing to make it start easier. If the release isn't working it could have to much advance for the compression and actually be detonating (preignition or spark knock in other words)

I'm of the mind that this is the right track. If it's turning over (ever) I don't think starter, unless I'm not getting the whole picture. I also had a carb issue once upon a time that allowed the cylinder to flood while sitting. Similar symptoms to what you described. Would not turn over unless boosted....as it needed the extra 'oomph' to overcome a cylinder full of fuel. Also smoked a good bit at startup (guessing all the gas washed the cylinder wall pretty good. [smilie=1:

[Petrol & Powder]

It's really not that complex. The cam is equipped with a pin that interacts with the tappet and opens the exhaust valve mid-compression stroke to release the compression. As soon as the cam shaft starts to spin, (like when the engine starts running) centrifugal force pushes a weight outward and that action removes the pin from the path of the tappet. At that point the exhaust valve opens and closes normally and full compression is achieved during the compression stroke.

The Automatic Compression Release [ACR] allows a smaller starter motor to start the engine but if the ACR fails, the starter motor will need to overcome the full compression of the engine.

The spring the holds the weights inboard at zero or very slow camshaft rotation is a weak spring. It doesn't take much speed at all to overcome the ACR and return the engine to full compression.

There is no ignition timing involved in the ACR on a Kawasaki small engine, it is entirely mechanical and it acts on the exhaust valve.

The OP stated the engine was turning over slowly, which can be caused by the starter working against the full compression of the engine during an attempt to start the engine. So once all of the potential electrical problems are eliminated (starter motor, battery, etc,) the next logical place to look is the ACR. Because the OP stated that the engine ran fine once it started, that also supports the theory the ACR has failed.

[Thumbcocker]

I think I have a new starter motor somewhere. I am guessing that the compression release would be a puppy mother to replace/repair.

[rockrat]

Pull the spark plugs and see how fast the motor turns over. If still slow, you know then its not the ACR. Check for corrosion on the cable at the starter solenoid and to the starter if separate from the solenoid. Also, the connections from the starter switch to the solenoid

[Petrol & Powder]

...........I am guessing that the compression release would be a puppy mother to replace/repair.

In a word, YES.
But;

A good place to start is to check the valve clearance (valve lash). If there is excessive clearance on the exhaust valve, the ACR will not work well or maybe not at all. So adjusting the valves (setting the backlash) may be all that needs to be done to correct the problem. if you can get to the valve covers, this isn't a difficult job on a Kawasaki.
If the ACR mechanism on the camshaft is broken, that's a major job.

And spinning the engine with the spark plugs removed will not tell you much. The starter will have no problem spinning an engine with the plugs out, even if the starter is weak. My experience with electric starter motors is they either work or they don't, there's not a lot of in between.

[Budzilla 19]

^^^^^^^^^^^^^^^^^^^^^ what he just said!!!!! If lots of hours on engine, valve lash will change. just my experience. Good luck.

[john.k]

My brothers mower had one of these engines ,rebuilt for head gasket leak once,was running well ,but recently it dropped a valve and wrecked ....seems wise ,he says ,to renew the keyhole type valve retainers and valves ,as a retainer fail was the cause of the wreck.His wife was running the mower,possibly there was a warning noise ,but unfortunately the motor was run to destruction.

[Rapidrob]

You said it was working normally then not. This rules out a lot of problems.
Basic trouble shooting is key. Look at simple fixes first.
Fuel: how old? Water in it? Fuel filter clogged? Tank strainer plugged? Remove it and try to blow through it. If hard to do it is clogged. A normal breath should go right through. Drain the carb. Make sure the fuel is clean and smells normal. Alcohol in the gas attacks the aluminum in the carb and causes all sorts of problems. Clean it if needed.
Linkage bent or missing to the carb and governor?
Air: Air filter clogged? Full of old grass/dirt/mouse nest? If it has a foam band on it make sure it too is clean. Try to start it with the filter off.
Spark plug(s) Remove them and ground them to the engine, do they spark BLUE? Orange is a bad plug. MANY of the spark plugs sold today are phony Chinese crap. They look real but are not. I've had Three fail this year alone,this has never happen in my 57 years working on small engines! Buy real NGK's their the best IMHO.
Make sure the pick-up coil adjustment is correct. A loose coil will cause problems.
Battery: As stated above check all wiring to ground and positive. Lawn mower batteries suck. Poorly made with a short life.Try jumping the battery with your car/truck or spare known to be good battery.
If these things all pass with flying colors, THEN check for a mechanical malfunction. Such as a lose/broken shaft key holding the flywheel in time. Hitting a large rock or branch can cause this.
Check the simple things first. It WAS running now not.Sitting all winter always has me checking all I have posted.

[Petrol & Powder]

What the OP wrote was that it was turning over slowly but once it started - it ran beautifully.

Because that engine is equipped with an Automatic Compression Release [ACR]; a malfunctioning ACR will result in the engine turning over slowly. (the starter is fighting against the full compression during the attempt to start).
Because the ACR works by slightly opening the exhaust valve during the compression stroke, excessive valve lash on the exhaust valve side will prevent the exhaust valve from opening when the ACR is in play (during attempts to start the engine). Once the engine is running the ACR is no longer in play and the engine will run fine. This explains why the engine ran "beautifully" once the OP got it started.

[1006]

Make sure the fly wheel has not twisted on the shaft, making the engine out of time.

I had that happen on a Kohlar Command engine, with the compression relief setup similar to the Kawasaki. It had the same symptoms you are having.

[Petrol & Powder]

From the OP:

"Our zero turn has a Kawasaki 24 hp engine. It is turning over slowly and will backfire sometimes. Replaced solenoid and battery. Charged battery fully. No change. Last week it started with the booster pack. Once started it ran beautifully...…………."

[Thumbcocker]

I am going to check the valve clearance tonight. Just got a set of feeler gauges.

[Thumbcocker]

Adjusted the valves to .004. IT STARTED!!
Petrol&Powder was right. :-D

[Petrol & Powder]

Adjusted the valves to .004. IT STARTED!!
Petrol&Powder was right. :-D

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