John Deere S240 engine misses

[mez]

I have a 2015 John Deere S240 with with a Kawasaki engine family: KAX.603N4CB. It only has 177hrs on it. When the blade is engaged and your cutting the glass the engine bogs down and sound like the blade are slowing down. I figured it was the tractor belt slipping so I replaced with a OEM John Deere. It still doing it. I only use ethanol free gas. Been fine all summer. I pulled on spark plug boot off one at a time with and without blades on and the tractor remained running. Any ideas?

https://www.dropbox.com/scl/fi/tq9r...ideo.MOV?rlkey=hrc412o4jeiqpa15lhts927im&dl=0

 

[MurkyAsparagus]

It could be quite a few different things.

When I've had issues like this, it's almost always been fuel related. Have you checked your fuel filter lately, is there water in your fuel, what do your spark plugs look like?

 

[mez]

It could be quite a few different things.

When I've had issues like this, it's almost always been fuel related. Have you checked your fuel filter lately, is there water in your fuel, what do your spark plugs look like?

Its fresh 93 ethanol free gas with 1oz of Techron fuel injector cleaner/gal added. Spark plugs looks good but probably original. Gas filter was changed around 150hrs. Runs fine with blades on if no load or cutting grass on highest cut level.

 

[MParr]

Air
Fuel
Spark
Air filter must be clean.
You need good clean fuel and it should flow freely. You said the fuel filter has 150 hours. It needs to be changed.
You must have good spark. You said the plugs were possibly the original. Change them and gap at 0.030".

 

[mez]

Air
Fuel
Spark
Air filter must be clean.
You need good clean fuel and it should flow freely. You said the fuel filter has 150 hours. It needs to be changed.
You must have good spark. You said the plugs were possibly the original. Change them and gap at 0.030".

Fuel filter was changed at 160hts.. So only like 27hrs on gas filter.

 

[ctechbob]

Has it ever had a valve adjustment done?

 

[Slick3914]

Check your gas cap vent…

 

[mez]

Has it ever had a valve adjustment done?

Nope. If it was the valves why does it only do it under load? I would think it would sound bogged down all the time??

 

[ctechbob]

Nope. If it was the valves why does it only do it under load? I would think it would sound bogged down all the time??

If they're on the loose side they won't be opening fully and it wouldn't be getting the proper charge in the cylinders.

If tight it would be lower on compression so down on power, although it would probably also be a bear to start.

Worth looking into at least, I think those have a reusable gasket on the valve cover.

Could also be a bum spark plug. Ignition systems on lawn equipment aren't always super strong, so a bum plug might be too hard for it to fire under load.

 

[MParr]

Fuel filter was changed at 160hts.. So only like 27hrs on gas filter.

It's a 2015 mower. The fuel lines are probably deteriorating on the inside.
The valves probably need adjustment.
Have you ever checked for trash or rodent nests around the engine cooling fins? There could be so many things wrong with a 10 year old mower.

 

[Slick3914]

If they're on the loose side they won't be opening fully and it wouldn't be getting the proper charge in the cylinders.

If tight it would be lower on compression so down on power, although it would probably also be a bear to start.

Worth looking into at least, I think those have a reusable gasket on the valve cover.

Could also be a bum spark plug. Ignition systems on lawn equipment aren't always super strong, so a bum plug might be too hard for it to fire under load.

This exactly correct, it’s possible the exhaust valves are too tight

 

[volk06]

When you engage the blades, at full throttle if you apply a tiny bit of choke, does it allow full rpms or does it start to make the engine sputter?

Had a similar issue on my parents x390 with a kawi, couldn’t get to full RPMS when mowing, it turned out the foam pre air filter was covered and the box was clogged with grass and dirt. In dry conditions, it doesn’t take make to plug those air filters, just a matter of hours due to the design of the filter box..

 

[TnT_M]

check your air filter, fuel filter and the carb. My guess is you have some debris in the carb or something wrong with the fuel filter causing the fuel supply to run lean, which shows up under load (blades on).

 

[userfriendly]

If they're on the loose side they won't be opening fully and it wouldn't be getting the proper charge in the cylinders.

If tight it would be lower on compression so down on power, although it would probably also be a bear to start.

Worth looking into at least, I think those have a reusable gasket on the valve cover.

Could also be a bum spark plug. Ignition systems on lawn equipment aren't always super strong, so a bum plug might be too hard for it to fire under load.

I had a “bum plug” straight from the factory in a X320 JD. After 80 hours I put iridium NGK BPR5EiX-11 in it.
Last year when I bought a second tractor with the same 726 Kawasaki engine in a Kubota, the first thing I did was change the oil, filter and spark plugs.

 

[wavinwayne]

It's a 2015 mower. The fuel lines are probably deteriorating on the inside...

This is worth checking. On my 2007 John Deere LA110 that is currently torn down, the fuel supply line had completely collapsed internally to the point you couldn't blow any air through it.

 

[The_Eric]

Bad or weak coil? Plenty of Kaws suffer from that..

 

[14Accent]

When you engage the blades, at full throttle if you apply a tiny bit of choke, does it allow full rpms or does it start to make the engine sputter?

Had a similar issue on my parents x390 with a kawi, couldn’t get to full RPMS when mowing, it turned out the foam pre air filter was covered and the box was clogged with grass and dirt. In dry conditions, it doesn’t take make to plug those air filters, just a matter of hours due to the design of the filter box..

This should be your first test. Coming from a dealer tech here: what you describe is almost guaranteed to be a fueling problem. Those Kawi's are extremely sensitive to fuel quality, and I've had plenty of customer's come in with this exact issue "right after putting in fresh fuel". Guess what... it's always the fuel.

Flip the deck on at full RPM and gently apply choke. If the engine smooths out and gets full power back, start by completely draining the fuel tank and lines then refill with fuel from a different source. If that doesn't solve the issue, you've got crud in your carb and it needs a cleaning.

 

[volk06]

I have a 2015 John Deere S240 with with a Kawasaki engine family: KAX.603N4CB. It only has 177hrs on it. When the blade is engaged and your cutting the glass the engine bogs down and sound like the blade are slowing down. I figured it was the tractor belt slipping so I replaced with a OEM John Deere. It still doing it. I only use ethanol free gas. Been fine all summer. I pulled on spark plug boot off one at a time with and without blades on and the tractor remained running. Any ideas?

https://www.dropbox.com/scl/fi/tq9r...ideo.MOV?rlkey=hrc412o4jeiqpa15lhts927im&dl=0

Any update?