I have seen anything from 225F to 375F listed as acceptable temps for a 2 stroke .90 size engine (the latter is from Dave Gierke's book on two stroke r/c engines), but as far as I'm concerned over 300F is getting pretty hot. The general answer I've gotten has been that it's going to vary from engine to engine due to manufacturing differences, glow plug, fuel/lubricant variance, mixture, etc., and just because your engine is a little hotter than some, that doesn't mean that it is too hot for that particular engine. I know this is vague, but I hope it helps.

Dave