Motorcycle Repair: 1972 sportster, shift gears, sitting on the bench

Question
Just bought this 72 sportster in pieces with rebuilt motor and trans but person says it wont stay in 4th or go into 4th gear is there any way to check if it is going into 4th and staying in with it being together to take down the rode

         Thanks Bill

Answer
If the motor is sitting in the frame you can remove the plugs and rotate the motor at the rear tire and shift the gears. You can do the same thing with the motor sitting on the bench and rotate the sprocket and shift gears.
Good luck and happy riding
Mike