i have a 2006 rancher 350 FE, i rebuilt the top end this spring (0.25mm overbore, new piston rings and gaskets) it was running good, then at about 500kms started leaking oil from the base of the head, i went in, fixed that, but now shortly after that (probably less than 50kms, it started smoking. what could it be? it is burning a lot of oil. Am i supposed to replace the head gasket any time i have the head off? could it leak through that? could i have rotated the piston rings? I didn't replace the valve seals when I rebuilt the top end, but i wouldn't think it would burn that much oil so suddenly. what do All of you think?