I have a john deere x720. you can mow for a couple of hrs(3-4) then it feels like it runs out of gas. surges real bad and dies. wait lets say 30 sec starts right up but only runs good for about 15-20 min and it dies again and it will sart again and run fine for 15-20 min. it has spark. it has new plugs and fuel filter. it has done this 3 days straight now. it has done it with a 1/2 tank and a full tank of gas.

Likely it's only running on one cylinder.

check your fuel filter

check for water in diesil change fuel filter see if that take care of it the next thing put a ignition coil on it, or then do valve job for damaged valves

You know the old adage, Keep it simple, lol.

I was mowing along on my LA145, which had about 200 hours on it, and it slowed down then died. Before it died, it was acting like it was losing power. It felt like it was only firing on one cylinder. I waited a bit and it restarted after a lot of cranking. I made a couple mowing passes, and then the same thing happened.

Because I have mowed commercially for many years, I know my equipment inside and out. This mower was in top running condition and should not have been acting this way. There were no engine misses, no backfires and it was not normally hard to start. I knew the carburetor was clean, the coils were good, and the plugs were new. The fuel filter was recently changed. I got off, lifted the hood and gave a general inspection of the engine compartment. I noticed the fuel filter was nearly empty. I pulled the hose off the tank side of the filter and saw there was no flow.

The gas should gravity flow from the tank to the filter, if the tank has a good supply of fuel. Not that I recommend this practice, but I have no problem with doing it myself....I wiped the hose off and blew air back into the fuel tank. It helps to take the gas tank lid off first. After I got a good flow of air going back into the tank (it required several lungs full of air, you can hear the bubbles) the fuel began to gravity flow back through the hose at a decent clip. This fixed the problem. There is likely silt build up in the tank and it settles at the output port blocking the flow of fuel.

The problem repeated itself several times last summer. Back at the shop, I used compressed air to blow the line clear. The problem has not shown up in quite some time.

Check your fuel cap to make sure it is venting properly. If a vacuum is being created, and no air is able to get into the fuel tank, it will prevent the fuel from reaching the carburetor.

check your gas cap ro make sure the air hole is not pluged, try running it without the cap for a few min ans see if that helps, you may also anve got some water in the gas and its at the bottom of the tank and sloshs around and ocassionaly runs to the carb
it mkite not hurt to drain the tank into a clean bucket let it sit for a short bit the four all but cup or so back in as water is heavery than gas
also when you have the tant empty maybe blow it out from the fuel line back to the tank look in to see if anything has come back into the tank

Check spark plugs are not fouled and properly gapped.


OHV engines require periodic valve lash adjustment.

Loosen fuel cap 1 turn to see if it will stay running.Theres a tank breather hole/vent in the cap and when it becomes plugged no air can get into fuel tank when fuel is used,can also be a plugged fuel filter.

Hi
That is a fuel problem caused by stale gas you will need to remove and clean the carb with carb cleaner.
Sam