Author Topic: V50 Monza - Front Brake Binding  (Read 244 times)

Offline agoldfish

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V50 Monza - Front Brake Binding
« on: March 18, 2021, 03:38:48 AM »
Morning all!!!

So, yesterday evening I did a little work on my Monza, which admittedly hasn't seen much action. Last winter i had it apart to replace the clutch and over last summer didn't use it much (because i bought another bike which I rode ALOT more) and then in the Autumn, my Neighbour reversed into it, knocking it over braking a Mirror, clutch lever etc in the process. The insurance company dragged their heels and then its winter again.

Sorry for the long preamble!

So after an Oil Change, Carb Balancing and a bit of cleaning I set off home from my workshop last night and thought, It's only 5deg C I'll make a little tour through town.

16 Miles later the bile was getting slower and slower and needed more and more throttle so keep going, till eventually, it stopped. I looked down at the front wheel and the right Brake disc is glowing!!! the Lever is ROCK hard and the Bike WILL NOT MOVE. I dragged it off the street and on to the Sidewalk and left it there at 2am.

This morning the Brake is free and I rode the bike 1 Mile to work without issue.

So, what is going on? I rarely use the front brake, relying more on the Linked brakes.


1981 V50 Monza Café
1982 V50 Monza in bits
1957 IWL PITY
1992 Ducati Supersport 900
1984 Vespa PX 187 Longstroke Motor
2003 Aprilia Mille RSV-R

Offline berniebee

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Re: V50 Monza - Front Brake Binding
« Reply #1 on: March 18, 2021, 08:34:51 AM »
A few things:
1:The brake lever may be need adjustment. If there is zero lever  play, the pads will stay in contact with the disk with light friction causing heat/expansion causing more drag causing more heat/expansion until the brake locks up. Easy fix- adjust the lever for some play.
2: This happens to many vehicles sitting for long periods: Brake fluid is hydroscopic (Absorbs water) so the sleeping caliper piston rusts and sticks in the bore. You apply the brakes. The hydraulic pressure is strong enough to budge the piston outwards for braking but the sticking piston doesn't retract, causing the friction/heat causing more drag until the brake locks up. It's caliper rebuild time. Check the caliper slide pins for dirt/rust/binding too. (I'm not sure if the Monza has them.)
3: Master cylinders sometimes go bad- but it's usually a leak, not sticking.
4: Something got bent when your bike was knocked over - disk warped?

Your question should be posted in the main discussion area- this area is for build projects. Besides, you'll get a lot more responses from people with more Monza expertise. (It might be moved by moderator anyways.)

Online pehayes

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Re: V50 Monza - Front Brake Binding
« Reply #2 on: March 18, 2021, 12:17:37 PM »
Most assuredly it is a dirty bore and hopefully you can salvage it by cleaning or replacement.  It is the result of a poor design.  As the piston moves, it coats the cylinder wall with a microscopic film of brake fluid.  Dust from the air sticks in the fluid and creates a nice gum.  Modern brake cylinders have accordion boots intended to minimize this issue.  Your old Monza is wide open to atmosphere.

When the dirt accumulates and the piston sticks, the rider feels a very sloppy/loose hand lever.  "Let me snug that up."  Wrong.  The loose  handle is a sure sign of the sticky piston.  By taking up the slack, you now prevent the piston from ever retracting fully.  The full retraction is necessary to allow fluid to flow backwards up into the reservoir.

You might start by removing the lever and using a Q-Tip and some alcohol to reach in past the piston and see if you can clean the bore.
Use some small needle pliers and cover the tips with a bit of protective tape.  You don't want to scratch the piston.
Reach in with your pliers and try to grasp and pull the piston backwards or outwards to it full retract position.
Find a way to move it back and forth to clean up the residual dirt and lubricate its motion.
Reset the handle and leave a small bit of freeplay.  If the freeplay increases, DO NOT be tempted to snug up the lever.

Otherwise disassemble to clean or replace the hand master cylinder.

I had the same issue with foot brake on V65C.

Patrick Hayes
Fremont CA

Offline not-fishing

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Re: V50 Monza - Front Brake Binding
« Reply #3 on: March 18, 2021, 12:36:44 PM »
On my basket case V65 SP and my Son's V50 III we rebuilt all the calipers and flushed the system. 

I also rebuilt the front master for the V65 but my son didn't bother he just cleaned it and flushed the system.

Because the V65 SP came in boxes I also replaced the brake lines with stainless ones.

Both of the bikes had spent a decade or more on the Coast of Washington so just the air caused some corrosion.

Of course the fluid came out very discolored when we flushed the lines.
Griso 1100
Rosso Corsa Lemans
1/2 a V50 III (with my son)
V65 SP - soon to be finished
'75 850T with sidecar - a new project and adventure

Wildgoose Chase Moto Guzzi

Re: V50 Monza - Front Brake Binding
« Reply #3 on: March 18, 2021, 12:36:44 PM »

Offline Stretch

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Re: V50 Monza - Front Brake Binding
« Reply #4 on: March 18, 2021, 07:32:51 PM »
Calipers can also get gummed up around the O-rings and not allow the piston to retract.

I had a Gold Wing that did that to me. Disassembled and cleaned the caliper, and that mostly cured
it. Caliper seals can also get stiff and not allow the piston to retract fully. That and the goo will seize
things right up. Disassemble and clean the caliper and master cylinder, and replace rubber parts as
appropriate. No shortcuts on this one......  :cry:

                                                            -Stretch

Offline agoldfish

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Re: V50 Monza - Front Brake Binding
« Reply #5 on: March 20, 2021, 08:02:13 AM »
First of all, thank you for all of the replies.

I managed to nip to the workshop today and have a bit of a nose about. I couldn't get the caliper off of the disc without releasing the bleed nipple a little to release some pressure which does point toward the master cylinder I think. With the Caliper off, pumping the lever did push the caliper pistons out but they retracted back to their original position, where as in my experience it is possible to pump them out. ??
The Brake lever doesn't appear to be adjustable.

The brake fluid does look a bit grungy so I think stripping and cleaning the lot might help. The front Brake has always been a bit ... wooden, feeling wise since the swap to braided lines but has never been a problem.
I have another couple of sets of discs in the workshop so i think i'll swap that one out to ensure its not warped after being so hot and i have a few new sets of pads somewhere too.

DOT 4 Fluid right?

As a side, or additional question, the brakes discs have, very slightly, different distances to the fork leg, the right side is closer by a couple of mm probably, I can see it without needing to measure it. So, I loosened all of the axel-related fasteners and the Tardozzi Fork Brace and AND the fork caps and let the fork fully compress - which I thought would "even" everything out but made no difference. As its a MONZA, there is a Spacer on the left side and the speedo drive on the right, should there be any other bits in there? It looks like a thin washer on the speedo drive side would even it out again, and i seem to remember there being one but am not really sure.

I find it hard to imagine that something got that bent when the bike fell over as it was effectively pushed forward off of the side stand, fell to left and landed on the Crash bar and bar end mirror. The Exhaust was untouched.

Thanks again!

Chris
1981 V50 Monza Café
1982 V50 Monza in bits
1957 IWL PITY
1992 Ducati Supersport 900
1984 Vespa PX 187 Longstroke Motor
2003 Aprilia Mille RSV-R

 

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