If you have a lot of carbon deposits you may want to try some Sea Foam (T) Motor Treatment added to the gas. I saw an old Sea King outboard motor in the trash (1950’2 I think) and picked it up to tinker with. It didn’t run at all, and I suspect that’s why the original owners pitched it in the trash. After cleaning carburetor, etc., and adjusting everything, it would run, but not well. It seemed to run fine for a minute or two then would “cough” and die. Everything I tried did nothing to help. I was about to give up, but I happened to look into the cylinder through the sparkplug hole and noticed a bunch of carbon on the top of the piston. After thinking about it for a month or two, I thought that the carbon might be heating up and holding enough heat to cause the fuel to per detonate and kill the engine. Someone at an auto parts store suggested I try Sea Foam to clean the carbon out so I got a small can from Wal-Mart and poured it in to the engine through the spark plug hole and let it sit for a while. I did this a couple of times as I recall. I didn’t expect much, but It cleaned out all the carbon and the engine fired right up and runs fine now. You can also mix Sea Foam with the gas occasionally according to the instructions and it’s suppose to keep things clean. Give it a try.