how does atk decide on there prices?
Let the bike warm up, after it is warm, rev it while watching your bottle. If the level starts to rise, or starts building pressure in the bottle, you have a blown head gasket. This could be a problem with your overheating issue as well. Other than that, just watch the bottle after it is hot, and see where/why it is leaking.
an air bubble would do the same thing. WHEN you get the new bottle and cap, make sure you completely bleed the system. you can crack the bleed screw on the cover but i prefer the sitting the bike up on it's grab bar. do this till no more bubbles come up thru the bottle when you sit it back down. might take 3-4-5 tries.