Brake problem 1200S - Ducati Monster Forums: Ducati Monster Motorcycle Forum
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post #1 of 13 (permalink) Old 03-18-2018, 12:31 AM Thread Starter
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Brake problem 1200S

Today was my first ride on my new to me 2015 Monster 1200S.

I bought this bike from Copart last July as a salvage bike with 6900 miles. It had been dropped on the RHS, the RH footrest mounting casting, lower triple tree and tank were the main damage. Not too serious really!

After riding for a short distance <3 miles I felt a fair amount of drag and the bike would slow un-naturally quickly on no throttle. I thought at first it was the rear brake, but on closer examination found it was the front. I let the bike sit for a few hours and prepared for a second short ride. When I pulled the front brake lever it came almost all the way to the handle bar.

First clue?

On the second ride the same thing happened, although at one point the drag seemed to reduce a little. When I got home the front discs were quite hot.

During the rebuild the entire front end of the bike, from the steering head forward was off the bike and rebuilt, but the front brake hydraulics were always intact, the same pads as came off the bike were re-used, master cylinder was never opened etc.

So what could be causing this brake drag? The front brakes work great! Almost too good!! But it seems that the brakes are staying on. I guess it could be hydraulic or mechanical.

I'm looking for suggestions and any help that may help me fix this so I can ride this amazing machine. Here is my list of possibilities:

Rotors not central in the calipers.
Piston stuck.
Master cylinder stuck.
Kinked hydraulic line.
Return flow blocked.
Too much brake fluid. Checked OK but removed a little.

I'm going to take a good look at this in the morning but would really appreciate any suggestions, experience etc

Many thanks,

Ian
SoCal
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post #2 of 13 (permalink) Old 03-18-2018, 02:28 AM Thread Starter
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One more idea . . .

Moisture in the brake fluid. The bike has sat for 8 months, although I am in SoCal so not the wettest climate!

I'll bleed all hydraulic systems with fresh fluid, just for good measure . .

Ian
SoCal
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post #3 of 13 (permalink) Old 03-18-2018, 04:24 AM
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Sounds like fluid is not returning into the master cylinder...not familiar with your brakes...but the pushrod into the master cylinder needs free play...as the fluid heats it expands and will eventually lock the pads to the rotor and catapult you over the bars...very dangerous situation!!!

Opposite of the pushrod there may be apear to be a screw that takes a flat head...if thightend fluid can not return to the reservoir...screw it all the way in and back it out 1/4 turn

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post #4 of 13 (permalink) Old 03-18-2018, 12:25 PM Thread Starter
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Hi,

Thanks for the suggestion. My first thought was something along those lines, but there is some information that suggests to me that this is probably not the case.

When the bike was delivered it was to a friends business, 5 miles from my home. I rode the bike, damaged, to my home and had no problems with the brakes. The distance was double to my ride yesterday when the brake problem showed up. During the rebuild the braking system was not disturbed, except for the calipers being unbolted from the forks, the master cylinder was not removed or worked on in any way.

The fact that when the system has cooled down it needs to be given one full brake lever pump to get the lever solid again leads me to think that it is probably a fluid issue, although not returning to the master cylinder/reservoir, or returning too slowly, is also a strong possibility, although with nothing changed its difficult to understand why.

I appreciate any further thoughts.

Ian
SoCal
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post #5 of 13 (permalink) Old 03-18-2018, 01:29 PM
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Absolutely check the adjustment screw I discribed before you ride again... during disassembly it can easily be mistaken and screwed tight....it maybe the old fluid that allowed you to even use it in the first place...you remove the air and the fluid doesn't return you WILL crash...if the adjustment is as it's suppose to be make sure it's not blocked with debris
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post #6 of 13 (permalink) Old 03-18-2018, 01:50 PM Thread Starter
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I will absolutely check the master cylinder, including the pushrod.

I'm missing something here so I need to go back to basics and check everything!

Thanks,

Ian
SoCal
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post #7 of 13 (permalink) Old 03-18-2018, 02:34 PM
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@ianashdown
Brembo has a brake recall. Check to see if your bike's VIN is on the list.
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post #8 of 13 (permalink) Old 03-18-2018, 04:59 PM Thread Starter
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I just checked, my bike is subject to the recall, I'll call on Monday to find out more.

I looked at the master cylinder to see about a pushrod that can be adjusted. The Picture below shows the arrangement on the 1200S. I've backed of the small adjuster nut a 1/2 turn; we'll see if it makes any difference.

Keep the ideas coming!

Ian
Socal
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post #9 of 13 (permalink) Old 03-18-2018, 08:38 PM Thread Starter
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Good news to report!

Breaking all the rules, I made two change at the same time! I backed of the pushrod in the front master cylinder and bled the whole system with fresh fluid, and my problem seem to be solved. I went for a very short ride, only 5 miles, but twice the distance that the problem occurred before, and had no issues at all.. I'll try a longer ride next weekend or maybe one evening if I'm home at a decent hour! I also bled the clutch system which seemed to have a strange take up point and the fluid was very grey- massive improvement! I've never had a bike where the M/C had a bleed nipple on it, but this is where I got most of the air on both the brake and Clutch.

BTW. I used Motul RBF 600 Racing Brake Fluid.

Thanks for the help and advice; I report back with any new issues!

Ian
Socal
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post #10 of 13 (permalink) Old 03-19-2018, 02:44 PM
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Quote:
Originally Posted by DarR View Post
@ianashdown
Brembo has a brake recall. Check to see if your bike's VIN is on the list.
This is Brian being glad that he has a 2014! The rest of the bike may fall apart because it's the first year but damn, my Brembo's are all good!

Ian, Was the fluid discolored brown or whatever? If you had enough moisture in the system maybe you had a half hydraulic and half pneumatic system when the water evaporated from the heat!

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