coolant foam question

I am looking into buying a 1997 yz125, it needs a top end soon but I noticed the coolant froths a bit under throttle and goes away like carbonation when idling... no discoloration it's a still clear red, and no obvious bubbles in the pumped water when revved... Is that quarter inch layer of bubbles an issue? Or will a new piston kit and gaskets cure it anyhow?

Edited by CTV_Paton

Sounds like a leaking head.

You say in one part that when you rev, it foams up anthen in the next breath, it does not.

But it sounds like the bike needs work.

yea when its revved the fluid flows clear, when you let off the throttle and the rpm's drop the fluid settles at the full level with a layer of foamy bubbles on top, and within some seconds the bubbles vanish. like shaking a bottle of pop only you see no bubbles until you stop shaking and there's none being purged with the cap still on.

could be a leaky head gasket, or as serious as a cracked jug (rare).

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