Darmah 1980 rear brake bleeding.

mcinj · Post by **mcinj** » Thu Feb 05, 2009 3:04 pm

Is there a trick to bleeding the rear brake on a Darmah? I had seen all sorts of comments about the difficulty of bleed in the front but it was easy. I just can't seem to get the rear master cylinder to pum at all. Someone suggested taking it off and raising it above the height of the caliper. I'll give that a try, any other suggestuions?
Bruin

Post by **BevHevSteve** » Thu Feb 05, 2009 3:24 pm

thats what you have to do, or I find it easier to take the caliper off and hang it with a piece of wood between the pads.............

Craig in France · Post by **Craig in France** » Fri Feb 06, 2009 3:20 am

mcinj wrote:Is there a trick to bleeding the rear brake on a Darmah? I just can't seem to get the rear master cylinder to pump at all. Someone suggested taking it off and raising it above the height of the caliper. Bruin

Hi Bruin,

For the second part of your question - like what Steve said.

However, if the master cylinder isn't pumping at all, then:
a) If the piston is moving in the barrel, either the seals on the piston aren't working; or the master cylinder piston is ok, but the pistons in the caliper are seized, and the lines are weak and expanding.

Or:
b) If the master cylinder piston isn't moving, then the caliper pistons are seized (or, possible but less likely, the line is blocked).

HTH

Craig

mcinj · Post by **mcinj** » Sun Feb 08, 2009 2:45 pm

After an afternoon in the garage I'm totally frustrated. For the record the lines are new Goodriidge from UK c/o my son, the master cylinder internals are new Brembo and the pistons and caliper seals are new.
Using Steve's technique I get large and small bubbles but never any fluid level drop, I did notice one thing, which I am not smart enough to know, should the master cylinder have two holes in the base, or the reservoir bottom. Mine has one all the way through and one that is started, but doe not break through into the bore. I seem to remember that my front cylinder had two holes. Perhaops the factory used another bleeding process they certainly couldn't make any money thuis way.
P.S. Steve I did take the caliper off and rest it below the M/C level all to no avail.
Regards Bruin.

Craig in France · Post by **Craig in France** » Sun Feb 08, 2009 3:37 pm

mcinj wrote:<snip> ...should the master cylinder have two holes in the base, or the reservoir bottom. Mine has one all the way through and one that is started, but does not break through into the bore. I seem to remember that my front cylinder had two holes.

Hi Bruin,

I can't go and check, but I'd be surprised if the rear master was designed to work any differently from the front.

Go here http://laverdapedia.com/forum/index.php?topic=40234 for an explanation of how the master cylinder works.

And then have a close inspection of that smalll hole that appears not to break thru into bore :-)

HTH and tell us what you find ...

Ciao

Craig

Post by **BevHevSteve** » Sun Feb 08, 2009 8:22 pm

Your mc does have 2 holes but you can't see as the piston is blocking one because you have probrbly not seated the expansion washer deep enough into it's bore. Meaning you probably have not installed the kit correctly.

mcinj · Post by **mcinj** » Mon Feb 09, 2009 4:13 am

Steve: Thanks for your response. The second hole definitelydoes not go through, I removed the M/C removed the plunger assembly and checked. The fornt or central one, goes al the way through but the back does not. If anyone out rhere has an old rear M/C perhaps they could check. Then if I have nothing to lose I could drill it through.
Regards Bruin.

mcinj · Post by **mcinj** » Mon Feb 09, 2009 9:04 am

Thanks everyone for your help, there are indeed two holes in the bottom of the reservoir, one is very tiny and was blocked with crud from twenty years of sitting. I broke a bristle off a wire brush and cleared it. The information about the operation of the master cyclinder from the Laverda web site was extremely useful. How did we do this without E mails? Once again thanks! Bruin.

baddean · Post by **baddean** » Mon Feb 09, 2009 2:58 pm

So, Bruin
Does this mean that you got it fixed??
Dean

Vince · Post by **Vince** » Mon Feb 09, 2009 8:37 pm

The bloke who did the report on the laverda site is doing a topend rebuild for me at the moment,got to love fussy mechanics,he has found lots to fix.

mcinj · Post by **mcinj** » Tue Feb 10, 2009 4:01 pm

Yes Dean I must admit that I was very happy to see the fluid level in the M/C go down at last, Thanks everyone.
Bruin.

Craig in France · Post by **Craig in France** » Wed Feb 11, 2009 3:10 am

mcinj wrote:Thanks everyone for your help, there are indeed two holes in the bottom of the reservoir, one is very tiny and was blocked with crud from twenty years of sitting. I broke a bristle off a wire brush and cleared it. The information about the operation of the master cyclinder from the Laverda web site was extremely useful. How did we do this without E mails? Once again thanks! Bruin.

Good news Bruin!

[After your previous post, I really didn't want to have to say, 'Go look again'

]

Ciao

Craig

geomoto · Post by **geomoto** » Thu Apr 09, 2009 9:59 am

The way we have been bleeding the brakes (and clutch) on our dirt bikes is with a bleeding tool (check Motion Pro). It is a large syringe comes with a number of adapters. You fill with fluid connect it to what is normally the bleeder screw, open the master cyl. and "push" the new fluid up towards the master. Quick and works very well. Watch out for that Motion Pro site, lots of way handy tools for you to buy!

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