Brake master cylinder woes.

[Christian]

My bike is an '01 M900 Dark which has cup-style reservoirs and gold master cylinders with the four-way adjustable levels. AFAIK the 900 Darks came with coffin-style master cylinders, so I'm guessing one of the previous owner upgraded these.

When I pulled her out of the garage this year to ride, the brake master was a little spongy. It got worse over a few weeks, but slowly so I didn't notice it. I checked the calipers and found no air bubbles, so I bled the master cylinder and it seemed better.

After a few weeks it got spongy again and I bled it again, this time more carefully. It was rock solid after this for a few weeks and then again it got spongy. I'm on bleed #3 now and it's about to need another. I'm thinking the master needs to be replaced.

Sorry for the long winded story - wanted to give an accurate background.

My questions:

1) Is it possible that the master on the bike is incorrectly sized and therefore air is getting into the system somehow? I'm wondering if a PO added it and bought the wrong one.

2) I've seen a few different sizes of the gold masters. How do I check which I have?

3) Assuming it's the master, should I just buy a new one, or is there a rebuild kit option?

Thanks in advance folks!

[Speeddog]

1) Yes, possible it's the wrong size, but it won't suck air because of that.

2) They're stamped, I don't have the 'code' at hand.

3) No rebuild kits that I know of.

[Christian]

Thanks Speeddog. I guess step 1 is checking for the stamp.

How do I know which size I need? Are the calipers stamped accordingly as well? Ideally I'd like to verify I have the proper size to begin with before I replace it. Looks like yoyodyne has masters in all shapes and sizes at somewhat reasonable prices.

[Howie]

I don't remember the whole code as it is stamped on the cylinder, but it is a 16 mm. bore and, AFIAK, in '01 all 900s came with pee cup masters.  If rebuild kits are still available http://www.yoyodyneti.com     will have them.  If not, a new master is not terribly expensive, or you might want to upgrade to a radial master.  Call and speak to Fred for fitment and advice. 

[DaFoose]

I have an 01 M900S and have the cup style. I think those were stock on all 900's that year. But don't know for sure

[Christian]

Thanks guys. I know Ducati likes to mix things up a bit with model switchovers and the '01s are the first injected models so it isn't surprising that they'd have the cup-style.

I'm tempted to go with a radial master, but then I'd need to buy a radial clutch, and radial calipers, and then new forks . . . it's a slippery slope.

Thanks again!