) as I spotted traces of fluid inside the outer dust cover. For £20 it was a small price for peace of mind. Saturday morning, planned to whip m/cylinder off, on the bench, thorough service with new piston and seals and job done. Right?Nope! Big mistake!
I'd reckoned without the moron(s) who'd had the bike before me - one of whom had obviously tried to futz with the rear caliper at some point - and failed abysmally. The bleed nipple loosened OK (I'd treated bits like this with a drop of diesel when I first got the bike as a precaution against seized threads
) and fluid flowed through it OK, along with air bubbles from where I'd opened the line ........ but the dratted thing wouldn't seal again.Ho-hum - caliper off this time, on the bench, bleed nipple out for a shufti .......................
I presume from marks inside the bleed port that there's a small ball of some kind that sits over the exit hole, and that shuts off the route to the main piston chambers when it's pushed down by the nipple being tightened. The ball was missing, the seat was damaged and the alloy thread about 25% chewed away at the top! I got around the leaking seat problem my simply making up a soft lead insert which deformed to the (interestingly novel) shape of the buggered valve seat when I screwed the bleed nipple back in, but I think a new caliper's on the books unless I can rebore and recut the knackered thread and either fit an oversized bleed screw from a car's hydraulics or turn something suitably threaded up on the lathe!!! I feel like boiling whoever butchered this bike alive in hot engine oil.
Slowly!
OK. The rear brake now works OK but is a still tad spongy for my tastes, despite flushing through a litre of DOT4 and being able to lock the rear wheel. The questions I have for the esteemed members are:
1. The rear caliper doesn't appear on Graham's parts lists. Given that Bill's going to tell me that the Grimeca caliper's shit anyway, what's a bolt-on substitute?
2. Am I missing something with the bleeding sequence? The chimp who was in there last obviously managed to get an air-free system somehow - so what's the trick? Remember I can't really reverse pump fluid with a syringe because of that buggered bleed valve with the lead insert ......
Ta in advance.
Bob.
