Originally Posted by Biker Biggles

One more trick to try on the curvy S model-----
Look closely at the master cylinder/brake lever assembly and you can work out that there is a high point in the system where the brake line bolts to the M/C.Air bubbles can collect there and not be able to escape into the fluid reservoir along that bit of flexi pipe.I got those bubbles out by unbolting the whole assembly from the handlebar and fettling it so the bubbles could escape.It was only the tiniest amount of air,but enough to make the brake a bit spongy.