I have not changed the cap. Can anyone explain what happens to the old caps? See a lot of people suggesting to change this.
Yes, there are bubbles in the reservoir. To me it seems like the problems is that the way from highway to work is “too short” for the bike to calm down. On my way home I have only had this problem on really hot days.
Could it still be the head gasket?
The spring gets weak or the rubber doesn't seal . Have you bled the system of air ?