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Breva 750 Rear Brake Master Cylinder

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Eibar-Jet200 View Drop Down
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    Posted: 27 Aug 2017 at 19:08
Hi all,

Ok, I have tried for ages to bleed the back brake after a caliper rebuild but with no real avail. I have replaced the black hose underneath but it just refuses to pump any amounts of liquid through.
I have tried pressure feeding from the bottom as I had no top that fitted to do it from the top.

So I am guessing it may be the Master cylinder.

Is there any "better" ones than the standard? Or do I need to buy a replacement master?

Thanks for any advice.

John   
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John
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telegraphroad View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote telegraphroad Quote  Post ReplyReply Direct Link To This Post Posted: 27 Aug 2017 at 22:51
I don't know if the rear m/c is the same/similar to the one on the v50 but if it is then there is a tiny pinhole in the top of the cylinder bore which acts as a fluid transfer port from one side of the piston to the other. If the rear brake is refusing to bleed then it could be that the pinhole needs clearing. I battled with a difficult rear brake for a while until I did that. IIRC there are actually two holes in the cylinder bore and the smaller one is really difficult to see even when you know where to look. You will need to shine something down there to see it from the inside. It is accessible from the outside if you remove the inlet elbow on the top of the m/c. After I cleared mine the brake bled through first try and was firmer than it has ever been.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Eibar-Jet200 Quote  Post ReplyReply Direct Link To This Post Posted: 28 Aug 2017 at 21:21
Thanks for that. I will have a look tomorrow.John
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Eibar-Jet200 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Aug 2017 at 16:40
Stripped it and it was full of gunk under the rubber bung on top. I could not blow through it even when pumping the piston. Nightmare!
So a new one from Gutsibits ordered but 7-10 days delay.
Aaaaaaaahhhhhh!!!!!
Lambretta it is for another 2 weeks!

John
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John
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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 30 Aug 2017 at 17:17
Sounds familiar, had this on my R80's front brake m/c, wouldn't bleed (albeit perversely the brake worked prior to being disturbed - don't they always?), stripped the m/c, full of cack and the cylinder walls corroded. Become scrap. Shocked

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Roadrunner Quote  Post ReplyReply Direct Link To This Post Posted: 31 Aug 2017 at 14:58
I had the same problem with my lil Breva. You can get new master cylinder from ebay as soon as you fit the new cylinder it will bleed straight away what joy
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Post Options Post Options   Thanks (0) Thanks(0)   Quote telegraphroad Quote  Post ReplyReply Direct Link To This Post Posted: 31 Aug 2017 at 18:59
Glad you got it sorted.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Eibar-Jet200 Quote  Post ReplyReply Direct Link To This Post Posted: 31 Aug 2017 at 22:16
Thanks.
I need to spend tlc on the Lambretta. Been about 4000 miles now.
2 more weeks little one.........
John
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John
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