sooooooooo...how hot is too hot?

[makenzie71]

How hot should the top end get on a 150cc air cooled Loncin lump? If the cooling fins get wet it sizzles pretty violently, but the bottom end isn't too bad...I can hold my hand to clutch cover for a three or four seconds so it's not unreasonable. I do have some heat concerns, though, and am going to get a temp gun after it later...just curious what I need to look for.