When I bought my Pantah 500 it was fitted with a replica PS12 brake master with an integrated reservoir. Probably a recreation of the original Grimeca part. Bought and fitted by the previous owner in april 2024. When I replaced the 44 year old original rubber brake lines for braided ones I wasn't able to succesfully bleed the rear brake. It turned out the piston was sticky and needed over a minute to come back in de original position. I decided to disassemble it but noticed after I removed the lever and the first rubber dust seal that there is no circlip holding the piston. Its a pressed in affair. No idea if they are rebuildable but I think not. I tried some contact cleaner in the reservoir to clean out the rubbers but this made it worse in seizing the piston completely. Soaking in brake fluid restored the previous sticky action. Any tips what to do with it? Currently I have an original Brembo MC with remote reservoir fitted (Moto Guzzi) but its piston size is 16mm and stamping on the pedal generates hardly any decelleration.
the original PS12 would have had a shorter nose, opposite end to the banjo bolt. they didnt make this master in a PS16 Whats that one in the box ? its obviously a reproduction If you have the original 12 they are rebuildable, i keep the piston and seal kits however you need to make or own a tool to fit the retaining washer that holds the hole lot together. Those reproductions seals tend to swell making the action tight, its not a huge problem in its self but the return spring they use is not strong enough, its noticable smaller than the original brembo item.
The one in the box is the sticky PS12 replica. The Guzzi PS16 with remote reservoir is currently fitted but with 16mm is way too big. I do not have the original Grimeca master unfortunately
