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V50III Rear Brakes |
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AdrianW 
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Joined: 05 May 2019 Location: Bristol Status: Offline Points: 1208 |
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 Topic: V50III Rear BrakesPosted: 12 Jul 2025 at 17:49 |
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Dear All, As the garage is (surprisingly) one of the few coolish places around here i have managed the spend a little time on the V50 project. This time its' the non-functioning rear brakes. I have managed to get most of the bits off, with the exception of the pipe that comes from the front LH caliper which is firmly attached to the alloy adapter at the M/C end.. I have the workshop manual but there's no substitute for experience - hence the questions. Question 1 Master Cylinder.. I presume the internals are meant to drift out from the rear end towards the lever. Mine is firmly stuck at present. There was virtually no fluid in the system, the brake lever did simply go down towards the floor!. I don't know what I'll find inside.. Do you actually need to remove the M/C lever? It seems to me to pivot well out of the way .. Question 2 Rear Caliper.. It has come off the bike ok, nipple free, pads out. Pistons may be jammed. What is the best way to free the pistons? Can you get away with not splitting the two halves? It's been a long time since I worked on disk brakes (had a Laverda 500 with similar but that was many years ago...) Courtesy of PO I have a Brembo rebuild kit for the rear M/C. All thoughts appreciated, Adrian Bristol UK
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Motty
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Joined: 03 Jun 2015 Location: South England Status: Offline Points: 306 |
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Posted: 12 Jul 2025 at 17:57 |
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Regarding Question 2, on the RD Forum the recommended method is to either hook the caliper to a working brake (possibly the remaining front brake) and use the front brake lever to pump the pistons out. Or to fit a grease nipple in place of the bleed screw and then use a grease gun to pump the piston out (this way sounds messy)
There is a last option of drilling the caliper behind the piston, tapping the new hole and then using a bolt to drive out the piston. As this leaves a tapped hole to repair, it is generally recommended only as a last resort Cheers Richard
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It’s more fun to try to ride a slow bike fast .....
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Motty
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Joined: 03 Jun 2015 Location: South England Status: Offline Points: 306 |
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Posted: 12 Jul 2025 at 18:45 |
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It's probably worth doing a search on here as similar topics have come up before (including some from myself) here's a link to one I was asking http://https://www.guzziriders.org/v35-rear-master-cylinder-rebuild_topic3205.html?KW=Brake+cylinder |
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It’s more fun to try to ride a slow bike fast .....
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c13pep
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Posted: 12 Jul 2025 at 19:46 |
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You can use compressed air to `blow` the piston out but I must caution that this method does work but there is no control over the velocity at which the piston will exit the cylinder. DO NOT STAND IN THE LINE OF FIRE !!!!
This method will work with both the caliper and the master cylinder, GOOD LUCK CHRIS
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you can`t have any fun in a straight line
Honda CB77 project |
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Brian UK
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Posted: 12 Jul 2025 at 21:42 |
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There is a conical washer which locks the M/C plunger in, this can take quite a thump to remove. I would suspect you have some corrosion in there too.
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Brian.
Better 5 minutes late in this world than years early in the next. |
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Guzzished
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Posted: 12 Jul 2025 at 21:56 |
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When employing Chris's compressed air method, wrap caliper in bundle of rags to catch the rapidly exiting piston.
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AdrianW
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Posted: 13 Jul 2025 at 12:09 |
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Many thanks all... I don't have access to compressed air so I guess that's out.. The front RH brake is functioning so I could try that for the caliper. I imagine that the LH one will be in the same state as the rear one so I guess that will have to come off next - time to get the Plus Gas out again.. Does anyone know the actual Brembo model for the V50 rear master please? Google brings up a whole range of options, most of which are going to be wrong.. Then I can do more searches.. When it cools down (my timber workshop with the vice in is like a sauna at present) I'll have a go at drifting the MC internals out.. Thanks again, Adrian Bristol UK
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Oboyles
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Joined: 10 Nov 2019 Location: West of Ireland Status: Offline Points: 35 |
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Posted: 13 Jul 2025 at 16:54 |
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There's a method where you put a suitably sized socket into the piston, and jam a ratchet extension in beside it also, and rotate it using a ratchet. The caliper needs to be held firmly in a vice or similar.
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Mike H
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Posted: 13 Jul 2025 at 19:01 |
I have done it with a tyre foot pump, and I think using one of those adaptors for air beds, believe it or not, pushed into the hole. Caliper was split so I did each half separately. However while it worked, it also destroyed the pump, it was rated at 100 psi max. but the required pressure was over that (it had a gauge) and doing this ruined it.  |
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"Chicken nuggets don't dance on a Tuesday."
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paulbricey
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Posted: 13 Jul 2025 at 21:01 |
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Same as Mike H, split the caliper first, spray with WD40/AC50F, block any 'open bits' inside the clamp area (I did by clamping an obstruction in the workbench), remove bleed and reseat with PTFE to prevent air leaking around threads, slightly crack the bleed, fix bicycle track pump on bleed nipple, wrap in cloth to catch piston, pump hard (I can get north of 160 psi on my track pump & that defo does the trick !). On side without bleed just need to hold pump head down hard ...
BTW the caliper is F05 Brembo....you can get 'replacement similar but not same' P32 - not sure if the locating holes are same..
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Griso 1200 8V, V50
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Simond
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Posted: 14 Jul 2025 at 22:21 |
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If you use oil, do be sure to clean it off before you put new seals in, seal material is not compatible with oil.
Sorry if granny, eggs etc.
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AdrianW
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Posted: 15 Jul 2025 at 08:40 |
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Thanks Mike, Paul & Simon.. I have turned my attention to the other half of the linked system - the LH front caliper! This was hard to remove as the pads were pretty tight on the disk. At present it's still attached to the hose as I cannot free the joint. Looking at the threads on the 2 mounting bolts this is the first time it has ever been removed.... The nipple undoes which is a relief, just the inlet to deal with now. Again there was virtually no fluid there, just some thin brown stuff that looked like coffee. As suggested I will separate both halves, I might remount it (and the rear one) to undo the bolts. Not a case of sucking eggs Simon, I had forgotten that! There's also copious amounts of easing spray around the place that will need removal.. Does anyone know if I have to remove the actuating lever from the rear M/C before the piston comes out? It looks like it may swing out of the way.. Thanks again, Adrian Bristol UK
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Chris950s
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Posted: 15 Jul 2025 at 09:06 |
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To remove the pistons I used an internal bearing puller, with the caliper half in a vice.
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Chris and Karen - Essex
2011 Stelvio NTX, 1974 950S (750S replica nearly rebuilt!), 1966 Triumph T100SS 59 years young this year! |
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paulbricey
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Posted: 15 Jul 2025 at 11:34 |
 I think it will swing out the way Adrian (on rear of Florida I managed to put a spacer under the pivot without removing it - taking slack out as adjuster wouldn't allow pedal to sit in good position.On V50 I had to take it apart anyway because spring was broken when I bought it. If I remember it's the front PS16 m/c that is a bit fiddley & requires pushing/friction fixing refurbed piston back using the old washer & a suitable drift (I have Laverda brembo repair kit instruction pdf that guided me - let me know if you want copy !). Not sure if rear is simple circlip holding it but guess you'll find out pulling it apart
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Griso 1200 8V, V50
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AdrianW
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Posted: 15 Jul 2025 at 17:30 |
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Thanks Chris, I had no idea such a thing existed (I knew about the usual internal/external pullers) where it expands to fit the hole! Yours looks like good quality (probably older) one, I will get one of the modern (Chinese) kits and have a go. Thanks Paul, I'll try drifting the piston out with the lever out of the way to start with. If you have the instruction pdf it might be helpful - do you still have a Laverda? I have had them in the past.. One good thing, I have managed to free the front LH caliper from its hose so (slow) progress is being made... Thanks again, Adrian Bristol UK
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AdrianW wrote: