i have a nc30 stripped for a rebuild project , engine out problem i have is the gearbox sprocket appears to stuck on the splines of the output shaft and wont budge at all even after using plus gas and using a drift/lump of wood on the sprocket . was going to try some heat carefully on it but wary of damaging the outshaft seal. can a puller be used or any other tips would be helpful

Cannot see why you could not use a puller to remove the sprocket. Also suggest a good dose of WD40 or similar might help.