Intermittent Kawasaki surge

[hanz63]

I have this customer with a Deere LX 172 that will run for 20-30 minutes fine , surge like crazy- sometimes die. Restarts and runs well cool. It has the external igniter, though they do not describe any ignition symptoms IE backfire, just a surge and power loss. I can't duplicate. Every time I check there is an easy fuel flow from the tank, the pump does its thing nicely. Have cleaned every bleed, every orifice in the carb- clean as a whistle. I am not smart enough to replace the o-rings and carb gaskets. Inlet valve couldn't look nicer. It just seems to me like a carb issue. I am missing something simple here I'm sure.

[KE4AVB]

This is why I have 5+ acres. Sometimes and I do every so often need just use the equipment to duplicate the customer's problem. In this case I would first drain the fuel tank and install a new fuel filter as it sounds a lot like water in the fuel. If you can let the fuel tank air dry. Since this has a rear mount fuel tank also check the fuel line for kinking as I had some where the line go through such tight bend that they eventually pinch off the fuel flow.

I have personal Bolens that does this everytime I get water in the tank and it doesn't take water much either. I can look in the tank and water patches that are no where near the exit hole but during use it sloshed around and find its way into the carburetor. The 30 micron fuel filter stops the water until there is only water then some it gets push pass the filter.

There is also another problem that I have been seeing the last years too. That is fuel boiling in the fuel lines on some mowers. Usually can see this at the see fuel filters. This cause vapor locking leading to lean burn surging. I done had two cases already this year. I thinking it is Winter vs Summer fuel blends.

[bgsengine]

I'd also want to consider possible afterfire solenoid failure when hot, besides the possible vapor lock KE4 mentions, and if equipped with afterfire solenoid, might check its power supply route (switch,wiring connectors, etc) experiencing a failure or high resistance.. and also consider operating location (hillside? Etc?) for clues

[38racing]

Might be a stretch but I had one that would start and run until hot. It was a pinched kill wire.

[hanz63]

No water but that doesn't mean he doesn't intermittently pick up something in the tube in the tank. I see that in X series from time to time. I keep thinking as everything out of the line and the carb are so clean that it wouldn't be debris. But something larger, could be. It seems to me that the solenoid was 86'd , but if it wasn't that could be an option. I cringe at working on the Deere harnesses this old as they get brittle plus who knows what has been done to them. I'll keep you in the loop.