[Petrolero]

Greetings:

I have a 757 Ztrak with 800 hours, this is a new mower for me, it's my first season with it. Works great, I bought it used from the JD dealer nearby and I've been thru it fairly carefully to clean the dirt plugging the fins, new hydraulic oil, engine oil, filter, etc, etc.

I've noticed that the fuel pump appears to be pushing very little gas into the filter, just a very weak stream. The filter is empty. The mower for the most part appears to run strong when under load, but last evening it started bogging severely. I suspected the vac line because its getting old so I replaced temporarily with a made-up line and it started running again. So out to mow I went. Started bogging again and I mowed with it like that for a minute or so and it straightened out.

So the question is, how much of a fuel stream should I see in the filter when running? Again, there is no fuel visible in the filter, just a very weak thread of gas coming in from the tank. Obviously, running the mower lean will run it hotter and these things are susceptible to overheating anyhow what with the plugging of the fins. I don't think the mower has been overheated, I have 85# compression in both cyls...

Thanks for the help!
BTW, these forums are super!!!

 

[Austen]

It sounds like it's not getting sufficient fuel pressure. I would test the fuel pressure and compare it to the manufactures's specification.

That being said, Kawasaki lists the fuel pressure as being 2.76psi.

Here are the instructions on how to test it, as outlined in the manual which you can download here: 25 HP Kawasaki Engine Manual - PDF documents. If it's not the fuel pump, then I'd procede onto checking the fuel pump regulator.

Disconnect and plug the fuel pump outlet pipe.​

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Connect proper pressure gauge to the fuel pump outlet pipe.​

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Turn the engine switch to the "RUN" position, the fuel pump will
operates. Record the pressure reading. Stop the fuel pump.​

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Remove the pressure gauge and connect the outlet fuel tube.​

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Disconnect the fuel pump outlet tube from the carburetor inlet.​

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Put the tube end in a graduated container.​

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Run the fuel pump for 30 seconds. Stop the fuel pump. Record the
container measurement.​

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Compare the readings to the specifications.
If low, check for clogged or damaged tubes, fuel filter, or fuel tank.
Replace faulty fuel pump.
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Minimum Specifications
Fuel Pressure 19 kPa (2.76 psi)​

Fuel Flow 180 mL/30 seconds

 

[Mark / Ohio]

I can't speak directly from experience with your engine but on my Kohler 15 hp. I would say the filter runs about 1/4- at most 1/2 filled with fuel while laying roughly at a 45 degree angle. Couple things I would check is that you don't have some debris laying in the bottom of the tank causing a partial obstruction. Also would check your gas cap vent is clear. When it bogs down just loosen the cap and see if it picks back up.

 

[Petrolero]

Greetings forum lurkers-


Well it's 7 years later... Bought the machine in 2007 with 770 hours - now it has 1200. Been a great mower other than hard starting. It's getting worse.



I've changed the diaphragm-model fuel pump, yesterday checked the compression after running the mower for a few minutes to warm it up - found 120# on the side with the key and throttle, 110# on the side with the parking brake - pulled the carb and cleaned it - not particularly dirty - had a few specks of dirt in the bowl. All passages were clear. Decided that hard starting might be due to that solenoid shut-off valve sticking partially closed so removed the needle and spring so as to remove the possibility- while I had the carb and intake manifold off I removed the cylinder shields and cleaned the crud off the cylinder fins- it was time - I used a pressure washer and engine degreaser- plugged the intake holes etc. I also cleaned the plugs while I had them out - they are pretty new.



I put it all back together and it fires right up - was jubilant. Always a good feeling to figure something mechanical out. Mowed part of my yard and pulled off to the side to blow off the debris - then was going to move the mower and it wouldn't start. "Curses! Foiled again!," to quote Mr. Whiplash...


So specifically what this mower will do is- it takes a long time till it hits - many times the battery is getting weak by the time I hear the first hit - once it does that I can usually get it to start but I have to keep the starter engaged as it's spinning up. Finessing the throttle is a necessity. Once it starts it runs great - lots of power, no complaints. It purrs like a kitten at idle.



One more thing I'm going to check is the strength of the spark and clearance between the coils and flywheel. Other than that, I'm at a loss-


Any thoughts from someone with a similar symptom would be appreciated. I'd like to not trade this one in - they're currently showing $4k to buy - which means I might get $1k from dealer if I were to get a newer one-

 

[Petrolero]

Just tried to start after sitting overnight - hard to start and nearly did not-


After moving it about 50' to shop I pulled one of the plugs and found no or very weak spark-


I'm thinking now that perhaps either incorrect gap on the plug or incorrect gap on the coil to flywheel is the culprit-


Working that angle this afternoon...

 

[Petrolero]

Hopefully the final installment of this missive- found the coils were nowhere near the 8-16 thou away from the magnets... might be why the spark was weak-

 

[Petrolero]

Bingo-



Adjusted the coil distance to the magnets on the flywheel and it starts right up with the first whirl of the starter.


Hope someone else can use this piece of experience-


Petrolero

 

[Mark / Ohio]

Thanks for letting us know what you found out! :ThumbUp: