Sid, pull the plug out and kick it over. See if its got good compression.
Then check all the electrical. While the plug is out, check for spark. Then check that fuel is getting into the engine ... is the plug wet?
Let me know further if you still have problems.
Daniel, so there is no confusion, Sid didn't get the engine, nor much of anything else we originally got from you. Sid's got some semi-auto motor in the MXB frame. I still have the 125cc motor in the garage.
BTW Sid there will be no oil in that motor. Top it up.