Log Splitter Valve maybe?

[TMGT]

I have seen the valve that shift the pumps stages get stuck, a lot of time from a little moisture in the oil and long sittings, common with log splitters.

 

[yomax4]

Is the Governor working properly? They are easy to mess with but not so easy to repair. I've seen them unhook inside the engine. I still think it's the 2 stage pump though.

 

[muddstopper]

Well, now that we know at what pressure the engine is stalling, I am going to change my opinion on the problem to a possible pump problem. I would still change the spark plug, just because I have seen that problem so often this year. It is possible that someone did try to change shift pressure on the pump. Look close and see if you tell if they have had the cap off the pump. You didnt say what size engine or pump is on the splitter. A lot of manufacturer's size the pump just barely big enough to pull their pumps at max low flow/high pressure. Trying to turn the pump shift point up could/would cause the engine to stall, especially if the engine already was down a little on power. Before I tried to repair or replace the pump, I think I would raise and lower the shift point pressure ( screw the adjustment screw in and out) and cycle the cyl a time or two to see if what ever is stuck inside the pump breaks free. If it does, you could then readjust the shift pressure to where it works best.