900 Monster Front Brake M/C

[beethoven]

Hi guys
My late 97 M900 has developed an interesting front brake feel. It feels slightly soft on first pull but hardens on second. All attempts to blame it on an air bubble have failed and my tech suspects the master cylinder. There is no shortage of stopping power and no fluid leaks.

Any other ideas appreciated.

If I get another second hand m/c are the 750 and 900 bikes the same or does the 750 have a smaller diameter? Are there any model year differences with the coffin style.

What options are there for after market units that bolt on and use the brake light switch?

Any responses much appreciated.

Regards, Al

[Howie]

All dual disk 4 pots are 16mm. bore single disk 4 pot are 13mm. and 2 pot dual disk are 15 mm. regardless of engine size.  It does sound like you still have some air though.  Bleed with the master reservoir as close to horizontal as possible.  When done, use a wire tie to hold the brake lever in the applied position overnight.  You can use any master of the correct size, but you will need to buy the switch that goes with it or an hydraulic switch.

[beethoven]

Thanks Howie
We have flushed and bled with bike on work stand  with cylinder horizontal and I have tied the lever to bars over two days twice with no change.
Will try again before looking for low cost m/c to try. Is there a physical difference between the different size coffins.

[ducpainter]

Thanks Howie
We have flushed and bled with bike on work stand  with cylinder horizontal and I have tied the lever to bars over two days twice with no change.
Will try again before looking for low cost m/c to try. Is there a physical difference between the different size coffins.

Try cracking the banjo bolt at the master.

[cencalal]

I use a vacuum pump type bleeder, and have never been able to get a good result without first removing the bleeder screw and wrapping it's threads with teflon tape, to keep from drawing air past the threads, instead of from inside the master or caliper.  While bleeding I tilt the master and calipers in several directions while tapping on them to dislodge trapped air.

[Howie]

Thanks Howie
We have flushed and bled with bike on work stand  with cylinder horizontal and I have tied the lever to bars over two days twice with no change.
Will try again before looking for low cost m/c to try. Is there a physical difference between the different size coffins.

The size is cast into the body, it will say PS 13, 15 or 16.  Coffin masters are inexpensive if purchased from the aftermarket.
https://store.bevelheaven.com/Brake-Related-Parts/16mm-REC-Brembo-Master-Cylinder-Front-Brake/
Or you could take this as an opportunity to upgrade.

[Speeddog]

The size is cast into the body, it will say PS 13, 15 or 16.  Coffin masters are inexpensive if purchased from the aftermarket.
https://store.bevelheaven.com/Brake-Related-Parts/16mm-REC-Brembo-Master-Cylinder-Front-Brake/
Or you could take this as an opportunity to upgrade.

If you're contemplating buying new, or even a used replacement, definitely consider the upgrade to a small-pivot master.
They are better.

[DarkMonster620]

taka a look hjere

http://www.ducatimonsterforum.org/index.php?topic=75149.msg1381808;topicseen#new

[Howie]

If you're contemplating buying new, or even a used replacement, definitely consider the upgrade to a small-pivot master.
They are better.

Yep!

[DarkMonster620]

If you're contemplating buying new, or even a used replacement, definitely consider the upgrade to a small-pivot master.
They are better.

yes, this too . . .

[beethoven]

Thanks for all the info.
I will continue to look for any air and try the banjo crack next week before contemplating new or used replacement. Have been riding  with bike like this for 2 yrs now.
Do you have any recommended small pivot options. I see a Brembo Gold Line model but probably out of my price range with switch and cup.

[DarkMonster620]

Thanks for all the info.
I will continue to look for any air and try the banjo crack next week before contemplating new or used replacement. Have been riding  with bike like this for 2 yrs now.
Do you have any recommended small pivot options. I see a Brembo Gold Line model but probably out of my price range with switch and cup.

Goldline wont break your bank . . .

[beethoven]

Good news
Cracked the banjo at the m/c and released air bubble. Now first pull is same as subsequent ones.

I'm happy with result as no money outlay and I prefer the look of the two matching coffins.

Thanks Ducpainter for being on the money again.

Cheers, Al

[ducpainter]

Even a blind squirrel finds an acorn every once in a while.

[Howie]

Glad it all worked out.