The cylinder ode not need to be taken off to check the valves.
Remove the cylinder HEAD with the head bolts on top of the engine.
The valves should be visible to you then.
There are two ways to unstick the valves.
The right way and the fast or "Half-fast" way.
The right way would be to also remove the carburetor and remove the valve cover. using a valve spring compressor, remove the valve spring. put some penetrating oil in the valve opening on the top of the piston, grab onto the valve with a rag and a pair of vice grip pliers. Twist and pull the valve out of the block. Then use a wire brush on a grinder to remove all of the carbon on the valve stem and valve face. Use a valve guide cleaner of the correct size to clean the inside of the valve guide. Reinstall the valve ..or if it is too badly worn replace the valve and grind the stems to correct specifications.
the fast way is: put some penetrating oil in the valve opening on the top of the piston and them make sure that the engine is turned around to the place where the valve should be in the down position. Then, lightly tap on the top of the valve...driving it closed..Then turn the engine over again..very carefully, to raise the valve again. Repeat this process until the valve no longer sticks up when you turn the engine over. Then pull the rope many times adding more oil every once in a while to lubricate the valve stem.
When you feel the valve will no longer stick, clean all the carbon off of the head and the piston, and then reassemble the head to the engine. Start the engine and it should work. The one problem with this method is that it may stick again sometime and you will have to do the job again.
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I am glad that you got it fixed..Similar issue though.