JD X500 25hp Kawasaki Engine Surges Under Load

[efultz]

I have a X500 - great tractor except for one really big issue. Sometimes the tractor runs just fine. Other times, usually after about 15 minutes or so, tractor will begin surging and stall under load (when blades are turned on). For a while holding choke will get it to stop surging but once under load it will, eventually, stall. I am, often, able to get it to run smoothly if I take the air filter completely off and sit on the tractor for about 2 to 3 minutes holding the choke and, gradually, lessening the choke. After a while the engine will smooth out. I have had this at the JD dealer who just cleaned things (not exactly sure which things). We have a bigger JD dealer who services the big tractors and I am thinking about taking this baby there on the theory that if they work on the big boys they should be able to resolve this little guy. From what I have read it sounds as if there may be something getting in the carburetor or fuel line? Fuel is good as I run this in the winter, also, with the snow blower. It has similar problem then. The thing is this does not always happen but when it does it is a real problem. And, sometimes, I am as far from the barn as I can get when it happens.

Thoughts what might be the issue? How can I resolve this? Other than this really big issue the tractor has been very good for us. We have about 5 acres of land including horse pasture and such. So, when the tractor is working it gets a workout. I keep it in the barn - not outside in the rain or snow (most of the time).

 

[oldnslo]

Since closing the choke helps it does sound like a fuel delivery issue.
Simple checks first:
1) Is the vent in the gas cap blocked? I.e. does the problem go away with the gas cap loosened or removed?

2) Is there some thing in the fuel tank that floats over and blocks the tank outlet?

3)These engines have a vacuum operated fuel pump. Is the fuel delivery constant? I check this by removing the hose going to the carburetor and placing theend of the hose in a container. Crank the engine over and watch for a consistent fuel flow. Is the gas clear or full of air bubbles?

4) Is the fuel line from the tank to the fuel pump old enough to be weather checked? This can allow vacuum leaks which will starve the fuel pump.

5) I believe this model requires or has the option for adjusting the valve clearance. If the clearance is to tight the valves can be held slightly open causing a lack of vacuum & compression. Do you know if this has ever been checked?

I would suggest getting it resolved ASAP since running to lean can burn holes in the pistons.

 

[efultz]

Thank you for your reply. I was thinking fuel supply could be a contributing factor. But, when I remove the air filter and sit letting it run, eventually, it smooths out. Maybe this is just coincidence and the real issue is fuel filter or other fuel issues. I will check that. Gaining access to the fuel line appears problematic as I believe it runs through the body under the seat. Unless folks know of tricks to gain access (or I am completely mistaken).

This tractor has a huge cover over the fuel tank - designed to allow filling the tank without a funnel (quite nice, actually). I will look but I never noticed any gas cap venting (maybe I just missed it)

I have been meaning to check the fuel filter - so I will try the trick of removing the fuel line and cranking to confirm steady fuel flow.

As for running lean - it runs great lot of the time. But when it does not it is unusable so we are not running lean since when the problem happens the only real solution is to take it to the barn and stop.
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Since closing the choke helps it does sound like a fuel delivery issue.
Simple checks first:
1) Is the vent in the gas cap blocked? I.e. does the problem go away with the gas cap loosened or removed?

2) Is there some thing in the fuel tank that floats over and blocks the tank outlet?

3)These engines have a vacuum operated fuel pump. Is the fuel delivery constant? I check this by removing the hose going to the carburetor and placing theend of the hose in a container. Crank the engine over and watch for a consistent fuel flow. Is the gas clear or full of air bubbles?

4) Is the fuel line from the tank to the fuel pump old enough to be weather checked? This can allow vacuum leaks which will starve the fuel pump.

5) I believe this model requires or has the option for adjusting the valve clearance. If the clearance is to tight the valves can be held slightly open causing a lack of vacuum & compression. Do you know if this has ever been checked?

I would suggest getting it resolved ASAP since running to lean can burn holes in the pistons.