I put a Zenith carburetor on the 154 LoBoy this Spring in place of the IH original carburetor. The tractor runs fine when it is cold, but after it warms up it will start to miss. I can mow for probably an hour before the miss starts. If I pull the choke out about halfway the miss will go away and the tractor will run fine with the choke out. Because pulling the choke out fixes the miss I'm thinking it is fuel related instead of a spark issue. I'm wondering if I'm getting a partial vapor lock that is causing this issue. With the Zenith carb the fuel line does run a little closer to the engine compared to the IH carb. This did not happen prior to putting the Zenith carb on the tractor. Any ideas on the cause and how to fix it?