Oil in the coolant - 2016 Beta EVO 2t 250

[Mikhail]

Hi all,

so I bought my first trials bike and wanted to give it some love before riding (new piston, linkage bearings, change worn items etc...). As I was draining the coolant, after about 300ccm of coolant a big amount of dirty oily goo started to run out of the drain hole.

Any ideas what this indicates? Damaged seal on the pump? Or head leaking pressure from the cylinder into the coolant circuit? Any other ideas?

Many thanks in advance