After some help, recently put forwards on my 07 Streetbob, the forwards included a new master cylinder, so got a new brake line made up and all went pretty well after Scotty gave me a tip on bleeding the rear brake cause I couldn't get any brake pressure.  Had taken the bike to work a couple of times (45k round trip), no problems except the lid of the master cylinder was leaking a tad and leaving a few mist drops on the front exhaust. I reseated the cover and took it for a run today to give it a workout as I'm going to Tassie soon and want everything aok.

Anyway got into town and was going down a long hill and the bike seemed to be losing power but what was happening was the rear brake was slowly coming on and then locked the rear wheel. The brake pedal was rock hard. Called a mate to bring some tools but by the time he got there the rear wheel had freed itself??, we still craked the front banjo and pumped out some fluid just in case. Rode home without using the brake except for the last corner without incident albeit there is not much pressure anyway. Any ideas??? I have heard of an hydraulic lock or similar but dont know what to do next.

Thanks guys, good advice. Was going to do that in any case, might use a whole container though and make sure. Cheers.

can also be too much fluid in the res' when the brake heats up the fluid expands and pressure builds up pushing the piston out, thats why it comes good when u leave it sit cos it cools down, even if it aint full it will still do it, try les fluid in the res cos the correct level is nearly 1/2 inch fronm the top of the res'. this is the most common brake locking cause ive seen.

Also check mastercylinder piston to pushrod clearance, any preload will 1/2 cover the feed/return port in m,cylinder.
have struck this once before when bleeding was a problem on a mates bike.