One of your assumptions must be wrong. What happened between the last time it ran and now? First, double check to see if the needles are open on the carb, a quarter turn open for the high speed needle and 1 1/2 on the low. If the carb has been apart, make sure the diaphragms are in right and the metering needle is not stuck.
And is your starter turning the motor over at its normal speed?
LAD Specialties customer / tony kart / rotax / kt100