Mower was working fine until I hauled it to another site in trailer. After unloading it I started it and it ran about 45 seconds blowing gas out the muffler. I have worked on this problem several times since last fall. I have cleaned the carb and jet and checked to ensure carb filled with gas, installed a new coil, checked the gap, checked flywheel key/timing, put in a new plug (have plenty of spark), cleaned exhaust ports and muffler, checked fuel line and primer, cleaned air filter and put new oil in it, changed the fuel. I can see now leakage around the lower seal. Compression does not seem to be great, but it was running fine before and started easy. Yesterday after installing the new coil mower started and ran roughly for a short minute, and would fire again. Today I went through everything again and it fired once or twice and smoked out of the muffler. Nothing else. After priming and choking the spark plug is damp but not wet. Looking for some ideas.