Chains Back tire wont spin forward!

[rob2223]

I just got a motor for a bike that was previously used and was given to me, i put it on my bike and got everything put together and the back tire wont spin forward. iv tried spinning it back wards and it moves okay then but it just wont spin forward. Please help, i really dont know engines that well so if someone could help me id really appreciate it.

 

[crassius]

look where the chain goes into the motor - sounds like it is binding right there