Seeking advice, integrated rear master cylinder for a T3

[earemike]

Hi all,

Picked up a non running tonti that had been partly “cafe’d”.

Any recommendations on a good integrated rear master?

I think some Ducati’s & Aprilia’s ran them (& a host of dirt bikes).

Figure I’d ask as previous owner started welding brackets & removing parts.

Appreciate any guidance,

Mike

[Moto]

Any recommendations on a good integrated rear master cylinder?

The original one is a good choice. I don't understand what your motivation is. Do you want one with a proportioning valve? If so, later Tontis had them. Guzziology discussed their differences.

(I think a proportioning valve might be a mistake. It tempts a rider to just jam on the rear brake pedal, while the no-valve set up encourages a judicious approach. But that's not your question.)

Moto

[earemike]

The original one is a good choice. I don't understand what your motivation is.

Moto

Apologies, I was looking for the path of least resistance- if that is to find an original one then so be it.   

[jwinwi]

Here's the OEM unit, for part number if nothing else. The proportioning valve on later models and manifold on the earlier ones was a separate part...

[Antietam Classic Cycle]

The T3 didn't have a "proportioning valve", just a manifold block to connect front to rear with a port for the brake switch as well. If that's missing, I have one that I'll give you.

I have a good used original rear master cylinder as well, if you're interested.

New reproduction master cylinders are available from several sources, here's one: http://www.mgcycle.com/index.php?main_page=product_info&cPath=110_112&products_id=2900

[John Croucher]

The piston size used in a master cylinder is determined by the the number of and the diameter of the pistons being moved in the caliper/calipers.  A too large of a piston will give you a solid lever/wooden lever with very little grab or braking.  A too small a piston will give you a mushy lever with bite. 

There is a web site and brake parts supplier called Vintage Brakes that has a ratio chart to help determine the correct size master cylinder piston. 

As far as linked and not linked, you are opening up an oil debate type of argument here.  Me, i will go with non linked over size piston with a wooden feel on the rear. 

If your bike was set up with linked brakes in the past and you decide to de link, the front master cylinder needs to have the correct size piston to work both front brake calipers.  Or a larger piston caliper since it previously only worked on caliper and now you are going to be operating two.  The rear, smaller.

[Antietam Classic Cycle]

If "earemike" is staying with the original configuration - linked brakes - then IMO o.e. parts or replacements of the same type/size are a good idea.

If he's delinking the brakes, then this rear master cylinder might be a good choice:
https://www.ebay.com/itm/Ducati-750-860-bevel-drive-NOS-rear-Brembo-brake-master-cylinder-with-NO-SWITCH/360446989620

[Stevex]

If "earemike" is staying with the original configuration - linked brakes - then IMO o.e. parts or replacements of the same type/size are a good idea.

If he's delinking the brakes, then this rear master cylinder might be a good choice:
https://www.ebay.com/itm/Ducati-750-860-bevel-drive-NOS-rear-Brembo-brake-master-cylinder-with-NO-SWITCH/360446989620

The above is the exact mc I used to de link my LM2 brakes. It'll need some machining to allow it to fit 'back to front' from the Ducati's orientation.
It is a PS12; original is a PS15.
Have you ridden the bike de linked? I find it so much better.
If the PO de linked the bike, you'll need a PS12 front mc as well if the de link was done properly, i.e front mc changed to a PS15.

[moto-uno]

  Just curious if your T-3 has a single or twin front brake ?  Peter

[earemike]

Thanks for the solid advice, I could have given more detail.

Bike came with twin disc front, old school grimeca front master, rear master on a welded bracket - unknown brand.

No Brake lines 

So far I’m guessing it was dropped, engine rebuilt around 2000 with the owner planning a cafe. Never got it running - sold on in 2015.

Next owner replaced carbs, welded brackets, fitted a seat, removed gauges etc. from where the carb cables were run (& other evidence) he’d never had a tonti before. He got it running before passing to a mate to rewire, after that he never had it running so I had the opportunity to save the old girl.

[earemike]

If "earemike" is staying with the original configuration - linked brakes - then IMO o.e. parts or replacements of the same type/size are a good idea.

If he's delinking the brakes, then this rear master cylinder might be a good choice:
https://www.ebay.com/itm/Ducati-750-860-bevel-drive-NOS-rear-Brembo-brake-master-cylinder-with-NO-SWITCH/360446989620

Thanks, I’ll look into this option first before chasing that original.

Appreciate you mentioning the original you have 

[moto-uno]

  FWIW , I've had a front master cylinder from an early 80's Yamaha XJ650 . With the brakes unlinked ( is that a word?) I found this master cylinder
gave great braking and feel . And they look good ,  . Peter