OK, A powertorque uses a computerised module for the ignition, so to get kick back, there isnt really timing that can be adjusted as such.
The two things that come to mind first for me are:
1)Issues with belt tension; as this mower uses a belt driven blade system, it could be that the belt is not holding well enough during starting, and therefore the inertis needed to kick the engine over is intermittent, hence why you will eventually get the blade motion to start it, but not innitialy.
2)Flywheel damage, By memory, this flywheel (underneath) uses a D shaped crank section, rather than a key, warpage or other damage to the flywheel can cause the timing to be slightly out, witch could lead to this issue when starting.
I would suggest looking into both at once, take the engine off, and remove the flywheel, clean it up, and inspect it carefully, paying special attention to how firmly it mounts back onto the shaft.
Then, once you have done this, and re-attached the engine, pay close attention to the condition of the belt, and action of the belt tensioner while you are re-attaching the belt. Make sure the belt is in good condition, and does not slip while you are trying to start the mower.
