i replaced the head gasket on my 1967 850 last October, and then spent the next 6 months scratching my head cos it wouldn't start ...anyway, we're 9 months later, alls well and running fine, but i might struggle to do 500 miles before winter lay up....should i retorque head bolts now (after only doing a hundred miles since new gasket) or wait until 500 miles are done (or the most i can manage before winter)....Adrian