I can start it up, runs normal, I'm just scared to ride it because the harder I rev more smoke pours out...I feel like its gonna explode or something. I changed the oil that didn't seem to be the problem. Could it be bad gas, crud in the engine? Should I flush the engine? It is a Tecumseh 3.5 HP Power Sport engine...I want to ride it but I don't know what to do to fix it...pleas help 