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Discussion Starter · #1 ·
I went for a 100km ride yesterday. It was a rather slow ride with no +100km/h speeds and no heavy braking. Not a single problem on the way but when I arrived at home again, at the last turn before my house, I noticed that I could pull the front brake lever just a little bit further then normal.
I stopped, pulled the lever again and was able to pull it even further. I released again, pulled it again and that time I could pull it all the way to the handlebar and had no brake power at all.
Since I was only 200m from home, I continued till I was home and had the same problem there.

1st pull: little stopping power but the lever could be pulled in further then normal.
2d pull: allmost no stopping power and the lever almost touching the handlebar
3d pull: no stopping power at all and the lever touching the handlebar with no resistance at all.

I went in, put my helmet and jacket away and went to check the brakes.
At that time (with the bike on its side stand) the problem was gone. The front brake acted like normal.
I checked the brake pads, brake lines, amount of brake fluid, leaks,... Not a single problem to spot.
I changed the brake fluid a few months ago, bleeded the lines properly at that time and had no problem with the brakes since then.

I made a short ride to test and didn't experience the problem anymore.
This morning, I made a ride again, did some heavy braking on the way and had no problem.
This afternoon, I tried one more time and again, had no problem at all.

Does anyone has an idea what could cause this (temporary) problem?
I assume the problem is located in the master cilinder but I have never serviced one (I don't even know these MC's are serviceable). It's the stock master cilinder (1997, 900SS, black Brembo MC with a separate reservoir, dual brake lines to each of the calipers, stock calipers, stock discs)
Maybe a faulty gasket on the piston inside the master cilinder? But why does that only caused the problem yesterday? I think if it was broke yesterday, it still will be broke today?

Anyone?
Thanks in advance!
 

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1994 Ducati ss/cr
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Here is what I'd try:
Hold pressure on the brake lever for a minute or so.
Try different levels of effort and speed of initial application.
Classic failing brake master symptoms are often a sinking brake pedal at a stoplight..
If OK, heat the master a little with a hair dryer and repeat the static pressure check.
next, bleed the brakes into a clean glass container and check for anything ugly.
Closely inspect the reservoir for particles too.
If all this checks out I would still consider a rebuild kit or a replacement master - How old is it?
I agree it does not sound like a bleeding or moisture issue, that leaves you with an intermittent
hydraulic problem in the master cylinder cups.

Good luck,
Jim
 

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To be honest once a brake master does something like that I change it. Just too much risk to take a chance on a 20 year old part that is so important and costs relatively little to replace with brand new. probably about 150-200 usd to upgrade to a brand new part. I get not every part needs changing and it may be fine after a flush but is is worth the potential?
 

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Discussion Starter · #6 ·
To be honest once a brake master does something like that I change it. Just too much risk to take a chance on a 20 year old part that is so important and costs relatively little to replace with brand new. probably about 150-200 usd to upgrade to a brand new part. I get not every part needs changing and it may be fine after a flush but is is worth the potential?
If the problem is in the master cylinder I'll probably replace that.
The reason I asked about this problem is that I don't know for sure it is the master cylinder that's causing this problem.
I never came across a problem like this before so I thought it was a good reason for asking. Maybe it's a well known common problem that I never heard of...
In fact, I never did any brake work except changing fluid and pads. Brakes are fairly unknown territory for me.
So it would be stupid to replace the master and then find out the problem is caused by the caliper, or the brake lines or so.

At this moment all fingers are pointing to the master so I'm gonna look into that and when I have any doubt about it's reliability I'll replace it. As far as I know it is still the original master so after 22 years it is probably about time to replace it.

Any suggestions on a good replacement for the master? No track use, just roads.
 

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Discussion Starter · #7 ·
I found some Brembo master cylinders at carpimoto.it for a reasonable price.

Brembo PSC15 and PSC16 for +/-€120.

According to the site the PSC15 is stock "for many Ducatis".

I know the difference between PSC15 and PSC16 is the diameter of the cylinder but is that 1mm really the only difference or am I missing something?



P.s. Yes, I saw the gorgeous RCS17 and 19 as well but they are twice the price of the PSC's, they will look a bit too fancy on a 1997 bike and they will be more than I need for street use I think.
 

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the 16 will have a shorter lever travel, but also a bit more wooden in its feel compared to the 15, which will be a bit "spongier" for want of a better term.

depends how you like it.
 

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Discussion Starter · #10 ·
Check your Owners Manual, Technical Data section. PSC 16 is correct, I believe.

belter is correct, PSC 15 would give a too soft lever feel under braking.
Workshop manual says PS15 is stock but if 16 is a bit less 'spongy' I'll probably go for that one.
Thanks!
 

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Sometimes the size (15 or 16) is cast into the bottom of the master cylinder body.
.
 

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it's usually stamped on the flat section next to the pivot pin. they went from 15 to 16 sometime late 90's i think.

my 851 had a 15, and i put a 16 on it from my guzzi sport 1100i. definitely felt better, but the 16 i fitted to my monster when i went dual was a bit wooden (like the bevels often feel), although that may also have been due to the pressure point being a bit further out that my hand would have liked.
 

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Replace it with what is oem for your bike, if the book says a 15mm & thats what you have replace it with a 15mm, -same goes if you have a 16 and thats what is called for replace it with a 16mm. -go back with what Ducati spec's for the bike--remember you and I are not smarter then the engineer's that designed the motorcycle--stay with the spec and all is well---deviate from spec and it's your ass. at least thats my 2 cents worth
 

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Always remember--what you to your own bike is your choice--if you screw up and then get hurt because of your own stupidity--it's your own fault---If you stay with the MFG. spec's then you know your good, --But if you follow someone else's stupidity and get hurt????? hummmm--nuff said---just because it will bolt on does not mean that it is the best option
 

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You can wedge a V8 engine into a bike frame--Boss Hoss as an example--but does that mean it's a good idea??? Me thinks the answer is Hell No
 

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91 manual says the first 1600 had the black 32/32 calipers, then the typical gold 30/34, both with ps15. 94> manual says ps16.
 

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No harm in trying different masters as long as you are prepared to be the test pilot and are willing to risk not liking the change. I would simply put the oem stock master on new to keep it original, if that does not matter as much then there are a number of brembo upgrades you can do.
 
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