moped suzuki ay50 has no power to move need some pionters

[olivers14]

Hello! i have a suzuki katana ay50 year 2001 morini 50cc engine  and i just replaced the crank main seals and now when i have put it all back the moped starts and moves its wheel in the air and accelerates but when i go to put it on the ground it will not moove on its own weight and simply dies 
i have cheacked the carburator rebuilt it, clean it also cheacked the spark fuel any leaks changed the spark plug and so on.
And nothing works! so meybe someone can give me some pointers or someone had a similar problem with theyr scooter 

[classacted]

remove exhaust and check port from piston (get the carbon out of there carefully). leave the exhaust off.
try it.
I had an issue with a fa50 where two cycle oil accumulated inside the block. the oil delivery system can allow it to drip in there (the hose goes right into the block) and when so much oil gets in there, it drowns the plug with too much oil.
you might not have enough compression. you didn't say how much you have.