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Hello LawnWorld,
I am new here but I have a 2010 Z960A zero turn mower, 72" deck, with 1050 hours that is starting to die after it sputters for a bit. This just started this past few weeks. The mower starts up and I get about 20 minutes in and then it starts to sputter. Sometimes I can kill the PTO and idle it down to keep it from dying, not always. Each time it does dies, I can start it back up, no issues. I always burn premium gas, no ethanol. What is causing this? See list of troubleshooting done. When I was checking sparkplugs last night, I noticed the PTO kill switch wire going up to the RH joystick has finally cut apart, I assume from wear. The last time I mowed with my backup, I went to try zero turn again, and I couldn't get PTO to turn on. Would this PTO kill switch harness wearing give me this sputtering issue? I plan to just bypass that switch with joining the two wires together vs. spending $70 on a new harness that I don't use the switch for anyway.

This spring
- New battery
- New sparkplugs
- New fuel filter
- New air filter
- New fuel pump this week

Last year or year before
- New coils
- New drive belt

Thanks everyone!
KG

I forgot to mention that I have removed the fuel cap when sputtering, and it does not change. I have played with the choke and it did not fix it. I have also zip tied the seat switch down, no change.

Debris in the fuel tank blocking off the fuel supply ?

Thanks, I did just blow air back through the fuel filter line, not filter, and I think it did help. I fixed the PTO wiring and mowed a bit two nights ago. True test is tomorrow!

Thanks!
KG

Valve adjustment wouldn't hurt. It's a yearly thing. 11 year old mower with a ton of hours. Pull the head/s, remove carbon from head and valves. Clean cylinder cooling fins all the way around the block. Looking clean and being clean are different things. Carb rebuild, retorque the cylinder head/s. Flush fuel tank and replace lines. Good paper fuel filter and shutoff would be nice. Little Turtle Wax on the deck...... Tire shine on the 20" low profile tires LOL.

slomo

Carburetor rebuild won't hurt. Also would not hurt to check the butterfly screws for tightness as I just ran into my second carburetor this year with missing screws. I having to pull cylinder one head on the Z920M here because of missing screw to make sure it is not embedded in the top of the piston. At least the screw is brass unlike the Kohler Courage sitting out there with the damage head from the two steel screws. One was still in the cylinder and the other is in the muffler.

Engine was randomly running rough due leaking transfer tube o-ring and trash in right side main jet so the carburetor is getting a complete cleaning and rebuild.

It is just a pain that I got verify that screw isn't in the cylinder. I got to get myself one bore inspection cameras but I wanting one that I can inspect through those 10mm plug holes. When I remove these butterfly (plate) screws I install them using blue Loctite. Also making the terminals at the fuel solenoid are tight. Now the ECU can cause the fuel solenoid to act up. I got two 830, 925, and 950 this circuit that failed. All four units has had bypass surgery because of this failure.

As cylinder head retorquing I have never done it in the 12 yrs I have been servicing engines here. I figured if it is done properly to start with it should be fine.

But I would pulling the engine shroud at the beginning of the Spring startup of the mower just to check mice beds and chewed wires. It happens during the the rest of the year but long term storage is usually when it happens. I just done my second Kawasaki engine with #2 cylinder head replacement due blocked cooling fins cause the valve guides to move and bending both push rods.

As wiring problem just repair the harness. The whole harness don''t have to replaced if you have the wire, terminals, and proper crimpers on hand. I don't the wiring schematic on the 960A as the closest ZTR under my wing is the 950M and it has about 2000 hrs on it and it done had ECU module failure which I had done a triple bypass surgery on it as it had as it had failed but I keep the safeties functional as intended.

Whatever you do don't remove the fuel tank pickup tube as it is a royal pain to get back in the right position. The last one took me nearly 30 minutes of trying but I had to replace its rubber bushing so it was necessary to remove it.

I've found some used mowers with one or two loose head bolts. Maybe someone's been in there before with no torque wrench??? Or you have a Briggs Intek, I would recheck every year or two, if it makes it that long before tossing the head gasket. LOL

slomo

The Z960A will have a Kawasaki FX921V series engine.

Good Morning,
So last summer after trying everything I could think of that I listed above, I ended up taking it into a dealership and they put an all new carburetor on it. That was the cure and it has been running fine last year and all of this year until this past mowing. The mower starts up fine, I mow for 25min and it starts to do the same sputtering. I turn PTO off and the motor runs just fine in any throttle position. After it sputters once with PTO on, then it happens again every few minutes of mowing. I have emptied the fuel tank, blow air back through the fuel pickup line, replaced with new premium non-ethanol fuel, and replaced the spark plugs again, still no change.

What am I missing? This has to be something simple with it starting up, idling, running fine with PTO on, until a heat cycle of mowing then the stumbling comes back. The mower has 1120 hours.

Any help would be much appreciate!
Thanks,
Kelly

Can be a failing ignition coil.

Note v-twins can run fine on just one cylinder when not under the deck load.

kdgraham said:

I did just blow air back through the fuel filter line, not filter, and I think it did help.

Click to expand...

Think about what you did. Blew back threw a line. Now any junk will be pushed back into the tank which might clog it up or eventually back where it came from, clogging that up. Not a valid test.

Thanks for the reply. I have changed both coils around 950ish hours. I would hope they would last longer than 170 hours.

I will check on the butterfly bolts and transfer tube O-ring that you mentioned and I haven't checked. Also I will pull engine shroud to check for debris around any of the cooling fins. Since the stumbling only happens after engine is warm from mowing, this might have some effect. I do leaf blow all my mowers after each use to keep them clean, but maybe underneath is not so clean.

This just seems odd to me as I have never had a mower do this under PTO, but when PTO off, it runs 'fine'.

slomo said:

Think about what you did. Blew back threw a line. Now any junk will be pushed back into the tank which might clog it up or eventually back where it came from, clogging that up. Not a valid test.

Click to expand...

You are correct, I need to get a camera to verify if there is any junk in the bottom of the tank as I thought the same thing. However when I would kill the PTO, the motor runs fine at any throttle position. That makes me think its not a tank/fuel issue. Thoughts?