when i get a chance i'll be making a 12v vac pump for doing things like bleeding brakes, i have a spare vac pump off my rangrover that should do the trick.

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XT 630 SUPERMOTO

GSXR750L KMX200

RF900 & GSX400X Impulse Projects
3.9 V8 Rangerover

Im struggling with my back brake too, quite possibly just me being a newb tho.

I managed to sort the front brake out no problem by filling the cylinder and bleeding,several times and iv tried to do the same with the back but i dont seem to be getting any pressure from the rear master cylinder. The pin which pushes into the cylinder seems very loose and I can wiggle it in all directions. Is this normal or do i need a new cylinder?

they all wear out at that pin and adjuster, if its really bad you wont be getting the full stroke of the piston so its prob not pumping as much as it should.

try winding it out to its max adjustment or take the pin out and pumping it direct.

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XT 630 SUPERMOTO

GSXR750L KMX200

RF900 & GSX400X Impulse Projects
3.9 V8 Rangerover

Two ways I have resorted to in the past, just to save my self some headache.

1. If you are just changing the hoses, take the caliper off the swingarm/fork and pump the pistons out, but not so far that they start to come out of the caliper: 1 cm per piston is plenty. Connect the new hose, nip up the banjos by hand and then, push the pistons back in. Fluid will go up the hoses and into the master cylinder. Then just reconnect to the swing arm/fork, torque up the bolts, open the bleed nipple and start pumping out old fluid, whilst topping up with new till the stuff coming out is clear and new...

2. If you have dismantled everything and you cannot pump out the pistons with the existing fluid, get a 20cc sysringe from a pharmacy, connect some clear PVC tubing, fill the syringe with brake fluid, connect to an open bleed nipple and plunge the syringe. Go easy and you get the same result as above. Once you have 1-2 cm of fluid in the master cylinder, nip everything up to the correct torque settings and top up the reservoir.

Either way done: 20-30 mins. When brakes have been bled/rebuilt, I always bungee the lever at the bar, so that the system is under pressure overnight. Not too tight, but enough to highlight any leaks and to squeeze air bubbles from the system....

If the lever is not tight in the morning then you have a problem. Wrap cloth around the joins and seals just in case as brake fluid kills paint work

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Adventure: it's an experience, not a style!
(so ride what you like, but ride it somewhere new!)

Iv found the problem, the piston inside the master cylinder has seized in what should be the full on position. The only way I can think of moving it is to attach the front brake hose to the cylinder and using the front lever to try and force it out. But of course this will mean id hve to bleed the front again.

does anyone have any other suggestions please?

Rob

hi there it sounds like the cylinder needs dismantaling and inspecting carefuly ,an air line would be the best way to get the piston out if it is stuck , but it should just pull out once any circlip etc is removed you may just have forced it up in the bore if you were pressing too hard trying to bleed the brake. if things look at all IFFY get a replacement cylinder DONT TAKE ANY chancers take care zigzag.

Just to let you know, I managed to free the piston in the end.... I tried an airline but didnt budge, also tried a heat gun but the piston must have been getting just as hot as the cylinder so that didnt work either.

Freezer! I put it in the freezer for an hour then it just tapped out. Iv cleaned it up and now its working just fine.

cheers for your advice though,

Rob