Gas Zero Turn Ran on Diesel

   / Gas Zero Turn Ran on Diesel #1  


Apr 11, 2023
Argyle TX
2023 LS MT240HE. JD S240. Honda Pioneer 520. Ford 8n. Ford 9n
Hi y'all, I need some advice regarding a zero-turn mower at our Church. A few months ago, a volunteer accidentally put diesel in a gas Bad Boy 747cc Zero Turn mower. He said that he ran it until it started to knock and smoke badly. Then he shut it off, and it sat for a few months. When I heard about the story, I wasn't too concerned since diesel in a gas engine usually isn't as bad as gas in a diesel engine. Last weekend I flushed the tank and fuel lines, checked the spark plugs, and replaced the fuel filter. After a little bit of a struggle, it started. It smoked like I expected and knocked, but I thought that it was just some of the diesel burning off. Most of the smoke cleared up, but the part that I'm concerned about is a bad knock did not go away. Is there anything else I should check? Any advice is appreciated. the machine only has about 70 hours so the situation is pretty frustrating.
   / Gas Zero Turn Ran on Diesel #3  
Silly question, has the engine oil been checked lately?
My question too. If this machine is being operated regularly by (presumably) volunteers who do things like put diesel in a gas engine, one might wonder what else these volunteers are doing (or not doing). Probably a safe bet that the oil isn't being checked as regularly as it should be, or that the right oil is being used at all times.
   / Gas Zero Turn Ran on Diesel
  • Thread Starter
Good question. I checked the oil before I started it, and it was on the dipstick but a little low. I honestly doubt it has been changed since they bought the mower two years ago. I'll probably do an oil change on it tomorrow afternoon.
   / Gas Zero Turn Ran on Diesel #5  
MY thoughts is if tractor was run on diesel and the combustion forces of diesel may have over pressured the rod bearings, the bearing and crank may be toast... Not exactly what you wanted to hear.... Or again it was run low on oil and again rod bearings and crank may be toast.....
   / Gas Zero Turn Ran on Diesel #6  
Or the diesel caused a lot of pre ignition which damaged the pistons. They make inexpensive bore scopes that can use laptops or phones as displays. Maye you could use one to get a look into a combustion chamber.
   / Gas Zero Turn Ran on Diesel #7  
Many yrs ago I accidently grabbed the wrong can while trying to finish up mowing in the fading evening light... mower ran rough and weak but I finished... wasn't till later I saw my mistake. Drained the tank and put gas in it and it ran for many yrs after.
   / Gas Zero Turn Ran on Diesel
  • Thread Starter
Yeah, I fear it caused some serious damage. The volunteer said he ran it until It began knocking and was low on power. This is why I never share my personal tractors, ATVs, or Trucks. At least our Church signed a contract a few weeks ago to have the property mowed by a business. Thanks for the help
   / Gas Zero Turn Ran on Diesel #9  
Those engines are real easy to fix. Not very expensive either.
   / Gas Zero Turn Ran on Diesel
  • Thread Starter
I considered pulling the engine and looking at the bearings. It's just a matter of how much money the Church is willing to put into it. I've rebuilt lawn mower and Ford 8n engines before, so I'm relatively experienced in fixing small engines.