i have a 50cc yamaha that won`t start ?

i have check the starter and the spark plug and found that gas was inside the engine and i dont know what to do anymore 

when was the last time it ran?

how old is the gas in the tank?

did you drain the carb?

oil level good?

does it have compression?

are you getting spark?

I'm sure I could come up with more questions but checking those things would likely help me and any other people help us direct you better. Let us know

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The small Yamaha engines are quite simple and following basic procedures will narrow the point of failure down.

In any case you should properly clean or better replace the spark plug, check the carby and ignition.

I agree with the above. And I'll add that if you have a two-stroke engine that has been sitting a while there may be a chance some gunky oil residue has stuck one of the reed valves open. Which would wreck your compression. Had this happen to me once.