250-500cc 2011 WR300 Coolant in Combustion Chamber

Hi all,

Over the last couple of weeks I've noticed a slight smell of coolant when riding.
The bike had started losing/using coolant but I ride in very tough terrain and boil it quite often
Bottom end has about 400 hrs on it and recently did a top end for only the second time.

I have had broken O'Rings on the head before and assumed that this was the cause but when I took the head off today the outer was perfect and the inner seemed loose but still in tact.

Last couple of times the inner was actually broken or perished which was an easy diagnosis.

I Have heard that the impeller shaft can also be an issue but I can't see how it would let coolant into the crankcase.

What are your suggestions? What else should I check?
Gearbox oil is clean with no signs of milky love.

This will give you a bit of an idea of my average ride.


View: https://youtu.be/HffZwE1Cepc


Stu

Oring for sure.
Carbon near the journal's showing leakage.

Cheap fix then mate, good stuff

Thicker o ring ?
Or put the head on some 400grit sand paper and a glass then lap it in.

New O'Ring went in with a smear of hi-temp silicone.
It retains the coolant in the radiators now...Bonus!!!
And it's easy to start again.

Living the dream Hope the fix lasts this time.