49cc Automatic Transmission Stuck in gear. HELP!!!?

[Boss]

OK so yesterday i got a 49cc Super Pocket Bike from my older cousin. it had bad gas so i drained the gas out and mixed some new stuff (fuel ratio 20:1) its a 2 stroke. i got it started for a sec but then it died and i tried to pull start it again but the rope wouldn't budge. and the back wheel wont move because the chain is being pulled tight from being in gear. i need some kind of help please i have no idea what to do. there is a R6 Symbol kind of thing on the side. please tell me something that's worth listening to.

-Luke