Early Blue Spot Issue!

[X-Ray]

'94 Blue Spot Servicing. Heeeelllppp.

Well I was hoping to have the '94 ready for our Mapleton Muster, but it wasn't to be. Had a couple of issues with the front brakes, as the bike had been sitting for so long, and required a full tear down of the calipers, and a new master cylinder kit. I did try to do the job on the cheap and just "cleaned" around the pistons without removing them entirely, but on the first test ride, I made it 3 corners from home and the front brakes just locked solid. Called Alena and she brought me some tools so I could get home. Time to get serious now. The pistons were pretty grungy, and the seals were shot, but a quick run on the buffer had the pistons gleaming again, all of the congealed brake fluid was flushed out, and the new seal kit from the UK was installed with red rubber grease. All back together this afternoon ( after the Muster ), went for another quick test ride, and WHAT??, got a bit further from home and the brakes started binding, and then locked again. The discs were hot as hell, so something was stopping the pistons from retracting properly. Back home again with some help from "my mechanic" again, and decided to inspect the master cylinder return hole again. Removed the little splash plate, and yes there was fluid spurting back when the lever was released.

There was nothing that was obvious with this, and then I realised when I first rebuilt the master, I had pushed the splash plate right to the bottom, had this blocked the return hole? I placed it around 1/2 cm from the base, and went for another test ride. This time much better, did a few long brake tests over 30 mins, and no more binding. The discs stayed cool so hopefully that is what the issue was, started to do my head in!

EDIT 2 days later :  Well, these blue spots are haunted. I have the front wheel off the ground, and 2 days ago I checked the front brakes, the wheel was locked solid. Bled the brakes some more, lever is ultra firm, NO hint of mushiness/ air in the lines. Wheel was spinning nicely, apply brakes wheel stops, spin wheel, apply brakes wheel stops, all good. Go to work today in the car, get home,  check the wheel just now, no spinning just LOCKED SOLID!! The only thing it could possiblly be is still air in the calipers and the extreme heat in the shed is expanding it, locking the brakes on, without me even touching the bike?? I'm really stumped.

[X-Ray]

Ahaaaaa! This is something I overlooked. Tony (Bones) from our group suggested the second little relief hole in the master cylinder may be blocked, and I said what second relief hole? Grabbed an old master cyclinder from the shelf, dug around a bit with a pin, and what do you know, there is a hole there. Can't remember doing that on the '94, thought it was just a blank. After digging around with the pin and dragging out some gloop from the hole, pumped the lever a couple of times and out the fluid came like a geyser. So, it wasn't air expanding and locking the brakes, it was the fluid expanding and not having anywhere to go with a blocked relief hole, locked the brakes!  

Thanks Tony, legend mate,