I tried starting it but it will not turn over, had a back fire, I checked the sparkplug looks fine, no burn marks as such. Don't know if it is the choke or what. Battery was taking out and properly recharged, All it does is turn but does not engage. Any suggestions?

If it backfired it could have sheared the aluminum keyway between the crankshaft and the flywheel. That will throw it out of time and make it not start. This is a common problem after a backfire situation.