250-500cc 2004 WR 250 w/ 300 big bore kit loosing coolant out overflow

Hey guys,

Another quick question, seems im loosing coolant out the overflow, happens pretty much at idle when not even hot, blip the throttle and a the amount increases.

The previous owner told me about the issue and had the orings in the head replaced prior to pickup. However it still seems to have the same issue.

Ive done a bit of research and it seems it could be either the radiator cap, another failed or incorrectly installed oring or a warped head.

Bike has good compression and starts and rides well.

Is there anything im missing? if its a warped head whats my options for repair?

How did you make out?