Kubota BX23s rpms drop then backfires and dies

Kubota BX23S Tractor Problems

My Kubota BX23s has developed a problem where all of a sudden the revs gradually drop and then it backfires and often dies. Sometimes after the backfire, it gradually ramps up the revs, but keeps going up and down. The tractor is two years old and I had a similar problem with no backfire after using the backhoe which turned out to be a seat switch problem. I have bypassed the seat switches and the problem is gone. Today I changed the air filter and both fuel filters and everything seemed fine as I have mowed for about 15 minutes and then it started again. The downside is that when it backfired, the mower deck PTO shaft flew off and hit the fluid filter causing fluid to splatter everywhere. Tomorrow I’ll clean up the mess and change the hydraulic fluid and filter. Any ideas?


First the “backfire” – there really is no such animal in a diesel – but I think I understand what you are describing. Since you have changed BOTH fuel filters – did you see any contamination on them? Since they are both clean now and you have purged the system and run normally for a while I would say you have a fuel blockage at the tank nozzle. This can be a real PITA to fix.

Or maybe, if you’re lucky, a restricted fuel cap. Question: does your fuel pump tick when the key is turned to make it work? While under the machine, get a large container and see if the fuel hose from the tank allows fuel to move freely into the container. As for the output of the power take-off, either it was not “wedged” in the shaft, or it broke. If that collar is “wedged” into the PTO shaft, it should never come off in a situation like that. Or just one?


Because of the shape of the tank, you would have to put an access panel in the center, and it is not easy to get to it. They are not that bad to remove from the tractor if you have to clean it. It looks a lot worse than it really is. Remove the roll bar, the floorboard, the rear fender assembly and the tank is facing you. In addition, it gives great access to clean everything.

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