Just finished breaking down the top end on my big bear tonight. I'm doing this because the fourwheeler was blowing a ton of white/blue smoke while running. Got it tore down and noticed the piston and rings appear to be nice and clean. so did inside the cylinder. The only thing I noticed was that the head gasket appeared to have been leaking and there is a ton of black **** and corrosion caked up on top of the valves.

Should I just take the head to a machine shop or a atv shop and let them look at it? Also is there anyway to tell if the atv has been previously bored over? I dont want to order a stock piston if I need a bigger size.