M769 rear master cylinder rebild

[alickswud]

Have any of you guys out there carried out a rebild on a 796 rear master cylinder?

I'm unsure as to the size and where to get a kit from

Any ideas are much appreciated

[Luddite]

I believe that the rear master cylinders on all the recent Monsters are ø 11mm.

You won't be able to buy any spares from either Ducati or Brembo but KTM and BMW dealers stock the parts you need. Try here:

https://www.motorworks.co.uk/vlive/Shop/Parts.php?T=6&Q=BRA36241

but maybe compare your cylinder to an actual BMW one first to make sure they're the same.

Here is some useful guidance on how to perform the rebuild:

http://www.atomicalex.com/?p=139

[alickswud]

Many thanks for those links.

I'm going to strip it down and try and see if it is pitted on the inside to see if it is worth doing a rebuild before ordering any thing.

I think that the spring may be buggered but i wont know until i open it up, thats a job for latter the weather is too nice to be in the garrage today.

[Darren69]

I don't think a new one is very much, about 40 odd quid so maybe not worth repairing.

[Luddite]

You're not alone in your problems, Alick. Have a look at this other thread:

http://www.ukmonster.co.uk/monster/showthread.php?p=545331

Garry has ordered a complete new m/c from Moto Rapido for £49. If you're sure the m/c is shot, you might want to save yourself the hassle of a rebuild and do the same.

The part no. should be the same as Garry's i.e. 62540041A but Moto Rapido can confirm that. Don't forget to claim your 10% discount as a UKMOC member.

Let us know how you get on.

[alickswud]

I had a play around in the master cylinder last night and it was a right mess. Failed to get the piston out becuse of the corrosion but i still think the spring is broken as i cannot push it in, even with a nylon hammer.

I've just been in contact with Moto Rapido for a replacment.

[alickswud]

It's all back together now, bled the air out of the system on the bench before re fitting the whole malarkey.

Note: make sure you put the brake line on the correct way around or you cannot get the master cylinder in and you have to take it all apart, re-assemble and re-bleed it all again, (fitted new brake line at the same time).

I am able to push the pads back in to the callipers now whereas before they wouldn't go. I don't know if the spring in the master cylinder is busted of it is a corrosion problem as i cannot get the white piston out of the master cylinder to check.

Once I get off my crutches in the next couple of weeks I’ll be able to get back on the monster and test the brake out.

Just new front discs to replace now as my right hand one is warped.

[Luddite]

Hope that has fixed the problem, Alick, and that you get to enjoy some good summer rides.

The fact that the white sleeve is difficult to remove suggests that there is corrosion in the bore (it should be a light sliding fit). If you want to look inside, see step 5 in the guidance I sent you a link for.

What discs are you going for? Stock, wavy, Gold Line or something else?

[alickswud]

Rear master cylinder is fitted and all seems good now i can ride again.

I gave up trying to get the white piston out, it was that tight.

A set of Brembo ORO discs have just arrived for the front, please see post in Braking.