If you recall, the tractor would run fine when cold, but after mowing for about an hour would start to miss. Pulling the choke out about halfway made it stop missing.
With the IH carburetor, the gas line comes in the back right in the middle of the carburetor. With the Zenith, the gas line comes in on either side. When I got the Zenith the gas line fitting with the screen was already mounted on the side closest to the engine so I left it there. My first thought on why it misses was that it was fuel related, and given that it only happens when the engine is warm made me wonder about a partial vapor lock. So, I decided to move the gas line to the other side of the carburetor. I removed the carburetor to change the gas line and while it was off I re-cleaned the bottom of the manifold to be certain the gasket could get a good seal. I also checked the radiator and the coolant was right at the top of the core so I added a little bit to the radiator to be sure all the fins were covered. I then went and mowed for about 2 1/2 to 3 hours. The tractor never missed at all.
The weather was a little bit cooler today than the last time I mowed, maybe 5-8 degrees or so. I'm not sure if the problem was vapor lock and moving the gas line solved it. Or if the problem was vapor lock and the combination of adding a little bit of coolant combined with the cooler temperature made it run cooler so that it didn't vapor lock. Or if the problem is some kind of intermittent electrical problem that just didn't happen to appear today. Or if I managed to get a better seal to the manifold with the carburetor gasket this time around. I'm not sure. I'll let you know if it happens again.
With the IH carburetor, the gas line comes in the back right in the middle of the carburetor. With the Zenith, the gas line comes in on either side. When I got the Zenith the gas line fitting with the screen was already mounted on the side closest to the engine so I left it there. My first thought on why it misses was that it was fuel related, and given that it only happens when the engine is warm made me wonder about a partial vapor lock. So, I decided to move the gas line to the other side of the carburetor. I removed the carburetor to change the gas line and while it was off I re-cleaned the bottom of the manifold to be certain the gasket could get a good seal. I also checked the radiator and the coolant was right at the top of the core so I added a little bit to the radiator to be sure all the fins were covered. I then went and mowed for about 2 1/2 to 3 hours. The tractor never missed at all.
The weather was a little bit cooler today than the last time I mowed, maybe 5-8 degrees or so. I'm not sure if the problem was vapor lock and moving the gas line solved it. Or if the problem was vapor lock and the combination of adding a little bit of coolant combined with the cooler temperature made it run cooler so that it didn't vapor lock. Or if the problem is some kind of intermittent electrical problem that just didn't happen to appear today. Or if I managed to get a better seal to the manifold with the carburetor gasket this time around. I'm not sure. I'll let you know if it happens again.
