Project Vento has begun: help wanted.

[ducwiz]

Here is an extract from the Moto Guzzi 1000G5 manual, explaining how to overhaul Brembo master cylinders and P08 calipers.

Have fun ;o)

Hans

[cooperplace]

Hi Hans,
Thank you. My m/cyl looks like that. I made a tool that resembles their drift, grinding flat a large nail, inserted it and hit it, again and again. The piston doesn't come out. There's no circlip holding it in place. I suppose I could use my 4kg hammer, but that doesn't seem right. If I fill the reservoir with fluid and work the cylinder in&out, and place my finger over brake fluid out port, no pressure is generated. So this m/cyl seems to be toast, but I cannot dismantle it to fix it.

There do seem to be expensive replacements from Moto Guzzi sites.

[cooperplace]

Mine looks very much like this:

https://www.eurojamb.com/products/moto- ... -1766-7050

except the reservoir is cast in and it doesn't have the external return spring.

[Ventodue]

Hi Peter,

Give me a little time and I'll send you the model number for a replacement Brembo m/c that you can use, if necessary. I had to fit one to my Vento in place of the AJP unit that it had originally with because there are no overhaul kits available for the AJP.

Don't quite understand why the piston isn't coming out. A coupla of sharp raps with a 16oz hammer is normally all it needs. Don't pick up the bigger hammer - at least not yet ...

Craig

[Ventodue]

Hi Peter,

Give me a little time and I'll send you the model number for a replacement Brembo m/c ... <snip>

Update to this:
1. It was Jon who pointed me in the right direction for the replacement unit , so I can do no better than quote him:

" ... the 12mm Brembo unit fitted to the Parallel twins was identical to the Brembo cylinder fitted to the Vento and they come up for sale fairly often, so should not be too hard to find."

So there's a lead . As it happened in the end, I went for one of these:
https://www.ebay.co.uk/itm/Ducati-750-8 ... XQ56ZR~CQj

You have to make up a mounting bracket, that's all.

2. As to getting the piston out, you may indeed have to hit it a bit harder . I say this because I have just removed the pistons out of a couple of old master cylinders I have here and yes, the retaining ring in both was a bit corroded and sticking

To give you an idea of what you're dealing with, it's the arrowed item in the attached photo.
(What you see on top is the retention system that uses a circlip).

[Dan C]

I recently had the same issue.

Before trying to tap it out I tried to un-seize it by sourcing a grease nipple that screwed in the outlet end of the M/C and pumping it full of grease. With a lot of effort it did move the seized piston but even after a couple of goes the piston was still very tight.

However it did tap out relatively easily.

So it might be worth trying?

You might also find this guide helpful especially in regards to reassembly......

http://www.laverdamania.net/Repair%20Gu ... Master.pdf


Cheers
Dan

[cooperplace]

Hi guys,

I tapped it harder and out it came. Piston is 0.500" diameter, which I think is the 12mm. Bore seems OK.

Thanks for the excellent advice. I'm looking forward to having this on the road before 2022.

[cooperplace]

On the rear brakes I finally got the m/cylinder assembled, with a new piston, and new caliper seals, and a new brake line. I filled the reservoir and followed the sketchy Brembo bleeding instructions, which amount to: put a hose on the bleed valve, run it to a catch container, fill the reservoir, open the bleed nipple a bit, push lever all the way down, close nipple, release lever, repeat until there is good lever feel.

Well, I've done this many times now. There's no longer air bubbles coming out with the fluid from the bleed nipple. But on tightening the nipple, there's no braking action. None at all. What am I doing wrong? Advice as always greatly appreciated.

Edit: turns out that after closing the bleed valve, if I pump the lever 5-6 times, braking comes good. Don't know what's going on but I'll take it. Feel is quite good now.

[Bob_Matthews]

It sounds like if you have to pump the brake, then there's still some air in the system. The air is compressible, whereas brake fluid is not.

Sometimes it's advantageous to remove the system complete and get the bleed nipple on the caliper higher than everything else, with the brake line slopping upwards and then do the bleeding - the air has to rise to the top. It only takes a small amount of air to make the brake action rather spongy.

[cooperplace]

It has ok braking but is leaking from the front of the m/cyl. It seems I didn't seat the seal properly.