Sticking rear m/cylinder piston

nickst4 · Post by **nickst4** » 4 months ago

Due to lack of use, my wife's 650 now has a sticking rear brake master piston that is causing the caliper pads to run tight to the disc. Obviously, the master needs to come off and be dismantled, but I see the outflow is at right-angles to the bore so it won't be possible to push the piston out from that end. Does anyone have any tips about dismantling before I set to and try? I've recently had to replace the hydraulic stop switch on the 1000 and know what a pain it is to bleed the rear on these bikes!
Cheers,
Nick

nickst4 · Post by **nickst4** » 4 months ago

Answering my own post! I now realise that the problem noted above likely means the recuperation hole in the m/c is covered, and the possibility exists of the back caliper and fluid overheating and the brake seizing on and locking the wheel. Not good, especially as I have suspicions that the rear m/c on the 1000 is going the same way. Repair kits seem to be available, but the price of an old-stock new m/c with no corrosion inside it is only twice the price of a repair kit. A replacement m/c seems to be the way to go, if I can find the correct model with side exit. I think it should be 11mm bore but must check, including the bolt spacing. All good fun!

Aussiejoe · Post by **Aussiejoe** » 4 months ago

Remove the circlip and see what the pistons does, could use compressed air to push it out, and I have heard of people pushing pistons out with a grease gun.

Aprilia released a service bulletin on how to bleed this brake system Aprilia service note 009-2007

andybaggies · Post by **andybaggies** » 4 months ago

I've also had the master cylinder seize and this caused a fire, yes a fire

, at the rear disc that took out the caliper.

As you say a new master cylinder is the way to go and yes you want the 11 mm model with the side exit but you also want the outlet from it to be straight. Here's a quote from one of my previous posts on here (viewtopic.php?p=38822&hilit=fire#p38822):

"Not sure this will be much help but I've found the old bill for my repair, from Bike Torque Racing, which included the brembo product codes:

11mm black master cylinder - 10477610, £50
Straight master cylinder inlet adapter - 110312710, £4
Rear brake caliper, P2 34mm & 84mm - 20695163, £125 inc pads."

And links to the first two items are:
https://www.carpimoto.com/en-GB/6211_10 ... -black.htm
https://www.carpimoto.com/en-GB/5203_10 ... aight-.htm

Bike Torque racing should be able to supply these.

andybaggies · Post by **andybaggies** » 4 months ago

Aussiejoe wrote: ↑4 months ago Remove the circlip and see what the pistons does, could use compressed air to push it out, and I have heard of people pushing pistons out with a grease gun.

Aprilia released a service bulletin on how to bleed this brake system Aprilia service note 009-2007

What can also help a great deal is to unbolt the caliper and secure it in a position higher than the master cylinder. It all becomes a bit of a logistical faff but does seem to work.

nickst4 · Post by **nickst4** » 4 months ago

Thanks for your comments, Chaps, esp. anybaggies pointing out that the reservoir inlet needs to be straight. I hadn't noticed that in looking for replacements. There are plenty of these m/cs on the Continent but not so many in the UK. You never know if the Customs people are going to get nasty about importing stuff...

monkeyrocco · Post by **monkeyrocco** » 4 months ago

I have also had this on a previous raptor 1000 it locked the rear so much that it burnt the disc The bike was under warranty they replaced everything and it did it again to the mechanic on the test ride and they had to replace it all again. When I got it back it sometimes worked and sometimes didn't air in the system. As you probably know it is easier to bleed if you remove the caliper and place it on the top of the disc.

monkeyrocco · Post by **monkeyrocco** » 4 months ago

Here is what I have done to my project with a Chinese master for under a tenner

nickst4 · Post by **nickst4** » 3 months ago

Hi People,
Just wanted to report on the success of replacing the brake m/cylinder on the rear of the 650. I got the new Brembo PS11/B cylinder (two actually, including one for the 1000) from a very helpful site, www.ducbikeparts.de. As expected, they came with the 90degree reservoir feed so I sourced the straight Brembo stubs from www.addictionmotorsport.co.uk. These stubs are pretty difficult to push into the rubber collar, even with rubber grease to help. Don't want them leaking though...

The bleeding went very easily with the caliper raised above the swing-arm, mostly because of the increased stroke of the new m/cylinder compared with the partially-seized old one. The brake now works well, and my good lady really enjoyed her ride to the Suffolk coast for a bacon butty on Sunday!

andybaggies · Post by **andybaggies** » 3 months ago

nickst4 wrote: ↑3 months ago Hi People,
Just wanted to report on the success of replacing the brake m/cylinder on the rear of the 650. I got the new Brembo PS11/B cylinder (two actually, including one for the 1000) from a very helpful site, www.ducbikeparts.de. As expected, they came with the 90degree reservoir feed so I sourced the straight Brembo stubs from www.addictionmotorsport.co.uk. These stubs are pretty difficult to push into the rubber collar, even with rubber grease to help. Don't want them leaking though...

The bleeding went very easily with the caliper raised above the swing-arm, mostly because of the increased stroke of the new m/cylinder compared with the partially-seized old one. The brake now works well, and my good lady really enjoyed her ride to the Suffolk coast for a bacon butty on Sunday!

Splendid - sounds like it all went swimmingly and it's always good when a repair is successful.

And who can argue with a bacon butty as a winners prize

with tommy sauce of course...