The rings are "free".
there is no difference with partial choke.
i checkd all carb's gaskets, they are all new , the engine has a total of only one hour work.
i re-tight the carb's bolts - no go.
the hall sensor is ajustable, it hadnt moved, i tried moving it to see if it will make a difference but it doesnt. i placed it back at its original position.

i really dont know if its an ignition problem or a carburation problem...