Well for what it's worth I think you either have air or moisture in the brake fluid.
It's hard to tell from the photo but does the fluid look a little bit cloudy
when you look at the sight glass ? If the fluid doesn't look clear and bright
then miosture is the problem and you should change the fluid. If the fluid is
OK then the brake needs bleeding. I have a YBR and can tell you that there is
no way to adjust the brake lever travel. One piece of advice is that if you don't
feel confident to sort the brake yourself then get a dealer to do it for you. You
have to be able to rely on the brakes as you may pay a much greater price
than an hours labour if they dont work when you need them to.