850-T3 Cali linked brake problems

Not been out on the old girl for a few weeks due to house DIY. Just doing a few checks and found that the brake light was not working on the linked brake. Pedal felt floppy too. Back wheel not fully braked when pedal at maximum movement.
Tried bleeding but could get no fluid to come out unless I pushed the master cylinder piston back using a screwdriver on the end face.
I think my master cylinder has gone U/S yet is hardly used and only about 20 months old.
Anybody got any ideas? Another new master cylinder?
All the best,

Hi David
Does your bike have the brake hose splitter on the rear nearside frame tube? On some T3 based bikes the splitter has the brake light switch too.
As both braking and lights are affected this may be a good place to start.
Does the front linked brake work? If so the master cylinder would be OK.
First thoughts
Best of luck
Steve guzzibrat2013-09-22 18:53:07

Hi Steve,
Yes I have the splitter on the near side rear of the Tonti frame. The pedal now has nothing left after my attempts at bleeding the system and just goes straight to the metallic stop. I think my master cylinder is done for, it does not really appear to move any fluid.
Cannot check the front brake, need 3 people: one to spin the wheel, one to put full weight on rear parcel rack to lift the front wheel off the garage floor and one to operate the pedal lever.

You can chock the sump, I use a bottle jack. (?) Rear M/C piston can stick, take side panel off and watch the end of it, if it doesn’t return fully or is slow to return then it’s gone sticky. In this state it’s impossible to bleed because, well, piston is not returning fully. To prove it (or not) you could get hold of the end of it with long nosed pliers and see if you can pull it out any further. If so that’s what it is. May help to rotate it a bit as well and it may start working properly again. Otherwise an overhaul kit is on the cards. Alternatively, if left for a long period rust on the discs can push the pads off, then it can be quite a job pumping the pistons back out again.

Master cylinder piston is moving freely with a strong spring return action. When operated by the lever from the foot pedal I seem to get little or no fluid movement out of the bleed nipples on the front or rear calipers. I can get some flow if I push the piston much further by using a screwdriver as a pusher on the end of the piston. Moving the foot pedal now offers no resistance.
All the best,

Does sound like the master cylinder has failed. What bike is this? As Mike mentioned above, you don’t need to buy a full master cylinder, just a repair kit that includes new piston, seals and spring.Are you still on the original brake hoses? The one from the master cylinder to the splitter can swell up and fail. That would give you the same effect.

Hi Don. Bike is an 850-T3 Cali from 1980. All the hoses were replaced with Goodrich braided hoses when I re-built the bike. It is less than 10 months from its first MoT and it is still catching me out with these daft issues.

If you fitted a new master cylinder 20 months ago, it should last a lot longer. Not sure what the warranty is on Brembo parts, but it would be wothwhile speaking to whichever of the dealers sold it to you. Even if they only give you a discount on a repair kit it’s a help.

Take a look at the brake light switches they are pressure switches, On the 76 V1000 (same configuration as a t3 there is the front pressure switch kinda between the front forks on the bottom, what the 'Mericans call a “triple tree”, To us yoke.

The rear brake pressure switch is on the left hand side rear frame just at the back of the side panel and often gets lots of crud.

i had brake problems when this one failed, It was a simple job to replace it, parts from Guzzi specialists OR car parts place. I always use PTFE tape on the threads then reverse bleed the system.

If there are no other leaks that you can see then look at the master cylOn the V1000 there is an extra outside spring pulling the arm back. behind the right hand sidepanel.

When pedal is fully up (there’s an adjustable screw and locknut between pedal and frame to set the position) how much clearance is there between end of piston and end of lever, should be minimal, but still some (what the adjuster screw is for), if ‘miles’, summink is wrong. Test two: take off reservoir cap and depress pedal sharply, you should get a small drop of fluid leap up into the air at dead centre of the reservoir, if not piston is not fully retracted, or even, the hole in bottom centre of reservoir is blocked (if so, piston cannot refill with fluid). (This also works on fr. reservoir too.) I agree though at 20 months old it shouldn’t be going wrong.

There is about 3-4 mm clearance between end of piston and the operating lever with all the adjustment taken up. I can discern no fluid movement in the reservoir chamber as I move the piston backwards and forwards. I think the brake light switch is telling the truth…there is no pressure being generated in the system.

My ongoing front brake problems included buying a new master cylinder. It didn’t feel right and didn’t work. I have a borrowed one from Ray on at the moment and all seems well. So buying new doesn’t necessarily mean you get a decent bit of kit, it’s probably made in China for peanuts and sold at a premium to hapless buyers like me!

You certain there is no air in the system? This happened to me on my Norge when it was unused for a bit. Bled the rear brake and a load of air came out, all fine since, as it was previously. Still a mystery how it got in there.

I thought I must have air in the system so tried to bleed it at the weekend. I could get no fluid to move through the pipes so no expellation of air (or fluid).

It does begin to look like a master cylinder problem.

Had the same problem on Annies Virago, bought a master cyl kit popped it to Mark at Twiggers who did it while I waited cost me less than going and buying a set of circlip pliers to fit the circlip and some red grease…easy best few quid i ever spent.

The kits are available out there gutsibits and Motomecca

Thanks GB.
I think I will ask Paul at Corsa to do similar for me.
All the best.

I am currently trying lubricant spray into the open end of the bore that the piston runs in. Hopefully this will encourage the piston to move further out.
Not holding out much hope!!

This deffo doesn’t sound right. I still think this means it’s not coming out far enough (piston stuck). If so, it will NOT be able to pump diddly-squat. Humour me and try ‘manipulating’ it with the long-nosed pliers, see if you can pull it out any further… (?) On mine a bit of ‘exercise’ like this and it was right as rain again. Until then then it would not pressure up while bleeding.

Removed the whole lot and will take it for repair as soon as possible. The piston is quite reluctant to move and stops about 6-8mm short of contacting the lever. I think that perhaps the spring is broken or has lost its temper. I have nearly lost mine!
All the best,