V65 Linked Brakes - Stopped Working Over Winter Lay Up

Technical Small Block V Twins (not new V7s)
1

My V65 has always had really good brakes. I haven’t used it for maybe 6 months (been riding the Lario). But giving it a once-over before putting it back on the road the linked brakes suddenly don’t work. The foot pedal goes down all the way with little/no resistance. I can feel the pads in the front caliper closing but when you release the foot pedal the pads they go back to their previous position.

There’s no apparent fluid leak but it feels like there’s a load of air got in. I haven’t tried bleeding them yet as I’ve strapped down the foot pedal to see if that does any good.

Any ideas please?

ta
stuart

2

Before you spend any money on things like a new master cyclinder, or brake braided hose, remove the front linked calipier from the brake disc, and rebleed keeping the brake hose as straight as you can, jamming a spanner or suchlike between the pads to stop them moving out to far, take your time, check there are no bits of rubber inside the master cyclinder cap falling into the fluid below, (happened with my V65sp), if you have the orginal brake hose still fitted there should be a tag round the hose with a date on it, maybe 05/85 for example, if so and it shows a very old date maybe new brake hose would be as good idea, fitting a new seal etc kit to the master cyclinder is no big job but take note of the order the seals and ‘o’ rings are fitted., keep it clean and dont rush when working on brakes.

3

Is master cylinder piston stuck inward, if so it can’t get fluid from reservoir. Had to free mine with long-nosed pliers, works now.
#2. are caliper pistons bare steel, if so could be rusted up.

4

There is a weirdness to hydraulics that doesn’t follow logically under close scrutiny. In my experience anyway. One oddity that I have experienced that must be unusual but would give your symptoms, was when the pad material bubbles away from the backing plates - thus giving this kind of sponginess. If you take the pads out and put something solid in there that would at least eliminate that one. And if that is the case - simples - new pads.