The stock brake on the Norton dates back to 1972. When it was first introduced in 1972, it was considered a milestone in brake developement, I even remember out braking other bikes into the first turn at Summit Point Raceway in WV in the late '70s on my first Norton, a '72 750 Combat Commando.
Later, it was considered to have a wooden feel and underpowered. One issue was as the ratio of master cylinder diameter vs caliper piston diameter was better understood, it was thought the 5/8" bore of the master cylinder was too big and 1/2" was better. Several people made kits to sleeve down the stock master cylinder and I installed one on my '73 about 15 years ago.
All was well for the most part, sometimes I'd have some brake fade during long downhills with lots of hairpins, so I learned to use engine braking, especially when loaded for touring.
(https://photos.smugmug.com/Adv-Old-School-Rally-and/i-qCTgxwt/0/XL/Old%20School%20and%20Meltdown%202016%20001-XL.jpg)
Last summer the master cylinder locked up a couple times as it got hot. Even just sitting in the sun, it would lock and I put ice on it to free it up. during a ride to Little River canyon ladt September, it locked up and I had to get a rescue.
The guy that made the conversion was no longer in business, so I had no idea about parts to try to fix it, so decided to go another route. There's a ex-pat Aussie in the Philapines building some nice stuff, so I decided to go with one of his kits.
http://www.tritonmotorcycleparts.com/297620485/category/146825/online-store
Stock brake;
(https://photos.smugmug.com/Motorcycles/73-commando/i-XCmW9J8/0/XL/2016-11-13%20001%202016-11-13%20001-XL.jpg)
Stock Disc on top of the replacement disc to show the diameter differance,
(https://photos.smugmug.com/Motorcycles/73-commando/i-Sx8F78T/0/XL/2016-11-13%20001%202016-11-13%20003-XL.jpg)
Adapter for the new caliper;
(https://photos.smugmug.com/Motorcycles/73-commando/i-mkDTkgD/0/XL/2016-11-13%20001%202016-11-13%20004-XL.jpg)
Caliper installed;
(https://photos.smugmug.com/Motorcycles/73-commando/i-HtMRjBM/0/XL/2016-11-13%20001%202016-11-13%20005-XL.jpg)
The kit included a new master cylinder, SS brake lines, 6 piston caliper, rotor, and all the hardware.
Probably overkill for a 90/90-19 tire, we will see.
It definitely has a cool look to it.
Wonder if he's using reman Tokico calipers in the kit or if he's sourcing some manufacturers in China (which supposedly the OEMs are now as well).
Supposedly he is making everything in the Philippines to his specs. He has a network of machine shops he is using and does his own quality control.
Colorado Norton Works sells a similar kit using a four piston Brembo caliper and master cylinder. It's priced at $1200, but the caliper is chrome plated and the fender brace has a big ugly bend in it.
http://coloradonortonworks.com/part-categories/brakes/#post-449