Runs rough when cold. Has power loss under heavy load. Has some black smoke from exhaust.
This sounds like you may have weak spark because you are seeing unburnt fuel coming out of the exhaust, which is black smoke. However, it could be possible that your valves are not seating correctly or that your valve lash needs to be adjusted. Or, your compression is low. First, do a compression check, should be at least 100psi. Second, bring engine upto top dead center, apply 30psi of air into the spark plug hole and try to listen for air weaping either out of intake, exhaust, or breather. This will let you know what valve is faulty or if your rings are shot. Third, check your spark with a spark plug tester. Place the gap a 1/2" apart and turn over engine. You should have a nice blue spark across the gap. If it is orange looking, then replace all of the ingnition parts.
Before starting your engine, check to see what position the throttle plate is in. It should be partially closed when you first start the engine and opens as the engine becomes warmer. Unless it's controlled manually. If it runs rough at open throttle and spark is ok then try to close the flow valve at the bottom of carb to see if it starts to run better. It's possible that it's just a flow problem.
If carb and cylinder flooded between uses this means that the float is not sitting correctly in the carb. Make sure that the float is aligned straight and that the rubber needle seat is in tact. This means that you have to take the carb apart.
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spark is good and Installed new plugs. Engine must be partially choked when running to keep it running smooth.
carb. and cylinder used to flood between uses before I installed a fuel shutoff
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