I have a 1976 John Deere JDX8. It has a 440 ccw engine. I have a problem keeping it running. It starts fine and runs good for maybe 10-15 minutes, and then just dies. when I am running it and it starts to die, I can shoot some ether into the carb and it will keep running. I have narrowed it down to a fuel problem of some kind. It has a Walbro carb on it. I put new fuel lines (clear lines) and a new fuel filter on it already. I can see the fuel running through both the in and return lines. The return line will sometimes of an air bubble go through it, but still full of fuel.
No I have not cleaned the passages. Do I just remove the high speed needle and the idle needle and make sure those passages are clean? Do I need to take off the lower part of the carb, and check the stack of plates that has fuel pump plate, and filter plate?
I read somewhere, possibly end seals are bad, is this what you mean? As far as repairing this old sled, I paid $50. for it about 10 years ago. I will probably junk the sled, rather than put much money in it. The rest of the sled is pretty rough.
I've had similar issues before and I found that it was the coils lost spark once the engine heats up the loose spark so once it shuts down check for spark as quick as you can if it were a seal it wouldn't run right from the start it wouldn't run good then just shut down if it were a seal issue for I have replaced a lot of seals in my day but the other gentleman is right if you sprat behind the clutch with starter fluid and it reves up you have a bad seal it could also be you filter is pulling something up and not allowing fuel then it drops back down once it don't have pressure but I'm leaning more toward coils hope I helped