Brembo brake proportioning valve

Moto Guzzi V7 Sport, 750 S, 750 S3, 850 T, 850 T3, 850 T3 California, V1000 I-Convert, V1000 G5, 1000 SP, Le Mans, Le Mans II, Le Mans CX 100, Le Mans III, Le Mans 1000, 1000 SP III, 1000 S, California II, California III, California 1100, California Jackal, California EV, California EV Touring, California Aluminium, California Titanium, California Special, California Special Sport, California Stone-Metal, California Stone-Touring, California Classic, California Touring, and California Vintage models

Created: 2016 October 12

Updated: 2021 January 22

Thanks to Harald Kragh for sending me this information via email. In Harald's own words and photos:

This winter I succeeded in disassembling and assembling the valve. And here are a few pictures of the components.

Parts to be replaced:

• O-ring: 18.77 mm × 1.75 mm EPDM
• Lockring (Sicherungsring Seegerring): 22 mm

Here are I my pictures

Thanks to Charles Cooper for sending me this information via email. In Charles' own words:

I came across an article relating to the connections for this valve but for the life of me can't find it again. The valve is the one with a round rubber boot approximately 32 mm diameter covering the end with spring piston circlip. The valve has a mounting flange with two 6 mm bolt holes 35 mm apart and is fixed on the left hand side behind the side panel. It has 5 ports: master cylinder, front caliper, rear caliper, brake switch, and 6 mm bleed nipple. I have recently overhauled my Le Mans 1000 braking system and replaced such a valve. I reckon it had been incorrectly fitted as at MOT the brakes were appalling. It was originally fitted as per the article advice with I reckon the master cylinder and front left hand caliper the wrong way round. I have checked several parts books and translated front, rear, master, cylinder from Italian and conclude this is the correct arrangement for the connections:

• F-ANT = Front left hand brake caliper

  In Italian, front is anteriore.

• MC-PO = Master cylinder connected to rear master brake cylinder

  In Italian, master cylinder is master cilindro and rear is posteriore.

• STOP = Brake switch

  (obvious)

• POST-R = Rear brake caliper

  In Italian, rear is posteriore.

The article has the front left hand brake caliper on MC-PO and the master cylinder on F-ANT. If you look at the valve the MC-PO connection is completely different from the F-ANT and POST-R brake connections, which are identical. The master cylinder connection MC-PO has a separate screw-in plug with a nylon diaphragm / filter and O-ring arrangement, which also makes sense.