I have a 2004 Prairie 360 4x4. It was used at my parents ranch a couple of years ago during which my father (having dimentia) put diesel in it. He ran if not realizing what had happened. It then sat for a long time until recently I decided to bring it back. This is what I've done to it.
1) I replaced the carburetor and set, new air filter, removed and flushed the tank, replace the battery. Results- it starts and idles fine but bogs and dies once the excelerator is depressed. I can get it to stay running so that it will accelerate by advancing the choke but it bogs hesitates and backfires as the throttle increases.
2) I replaced the coil thinking that it was weak, not able to provide spark under load. Result- none, no change in symptoms.
3) I checked the air intake flow for obstruction by removing the filter and air box lid. Result- none, no change.
4) I disconnected the belt sensor that activates the "limp-mode" thinking it was causing the problem. Results- none, no change.
Any suggestions?
​​​​​​Are there sensors that could be causing this problem?

 

I would do a compression check first, if that is OK then look again at the carb to be sure it is jetted properly....the airbox and all its coverings are required to be in place for the factory jets sizes to work. Compression may be bad due to diesel fuel but mabey not depending on how much was added to the gas.
Jump the spark plug wire and see how blue the spark is....if orange then it is weak, needs to be blue to be hot enough. let us know what you find.

 

Diesel is just oil, and will not affect running once cleared out. In fact I recon it will have been better for the original carb to have been full of Diesel when laid up than Petrol. Clean the old carb out and try it back on.

 

I was thinking same on the diesel as I would rather have it sit with diesel than gas.

OEM type new carb?

 

My only concern with diesel is that it is so much thicker than gasoline that if it was a high ratio of diesel fuel it may have raised the compression rate so high as to damage the rings and drop the compression of the engine....have seen it happen some years back. Running a compression check wont hurt anything and tell the owner the condition of his engine before he looks at other things.