why kickback afflicts cold engines?

Kick back occurrs when you have fuel vapor and spark before piston gets to top dead center. Electronic ignition suppose to prevent this during starting. In cold weather moisture somehow could cause malfition either inside ignition module or flywheel starting trigger during 300 rpm or so starting signal. I would check the trigger at flywheel to make sure it's clean and moisture during cold weather does not cause a small water molecule freeze. Cold weather sometimes causes electronics to behave unusual.

Next time preheat the engine and components a little with heater when weather cold and moist and see what happens. 

Don't keep allowing this engine to kick back. It WILL ruin your sprag clutch on the starter setup and you'll have to pull the engine and desassemble the back end to fix it. Get the kick back issue fixed soon. This can be caused by more than one thing. Poor starting technique, poor carb sync, sometime a primer setup vs a better choke setup, a weak battery, ect... These iems are the most common.

READ CAREFULL STARTING PROCEDURE ON COLD WEATHER IN YOUR POH, PILOT OPERATING HANDBOOK.

WHEN YOU PUT THE CHOKE ON THE THE THROTTLE MUST BE IN CLOSED IDLE POSSITION OR THE CHOKE IS USELESS. THIS CHOKE IS NOT LIKE THE OLD OR NEW CARBURATOR ENGINE SET UP. 

AFTER THE ENGINE STARTS IT WILL RUN RUFF SO DISENGAGE THE CHOKE AND GO TO RECOMMENDED RPM FOR WARM UP.

DURING HOT WEATHER PROCEDURE IS SAME BUT THE ENGINE USUALLT STOPS SO YOU DISENGAGE CHOKE AND DO A NONE CHOKE START. 

REMEMBER THROTTLE ALL THE WAY CLOSED WHEN CHOKE IS ENGAGED AND HOPEFULLY ALL ADJUSTMENTS ARE CORRECT.

Quote:

"WHEN YOU PUT THE CHOKE ON THE THE THROTTLE MUST BE IN CLOSED IDLE POSSITION OR THE CHOKE IS USELESS."

This depends on where the engine idle rpm is set.

Thanks for answers. I know 912 starting ops and importance of carbs and choke sync , charged battery etc.

The original question was why kickback occurs mainly with low temp even with the same cranking speed of summer and soft start cdi (same 4° btdc fixed in summer and in winter)

the only think i can imagine is mixture condensation on cold manifold due the low temp (mixture leaning) but during winter gasoline formulation is more volatile to compensate....

seing the multiple upgrades (soft start, flywheel) and sprag clutch design modification on 912is i think original 912 sprag clutch design is on the weak side and rotax'd offer a big discount on this spare parts (lawyers rules..)

Last question. I heard of some cases of sprag cluth housing coupling with crankshaft damage (with orrible expenses to fix).  Any infos on that?