Loss of pressure front brake handle

Good Evening,

Just got back from a 700 mile ride this weekend. Bike ran great ... but ... three times over the weekend, I grabbed the front brake and there was no pressure. This loss of pressure would happen only once and when I grabbed it quickly a second time, it was fine. But it happened three times and that is a little troubling. Any notion on why this might occur on my 2012 1200RT? Thanks for your input.

Wishing you a safe ride.

Bob

Good Evening,

 

Just got back from a 700 mile ride this weekend. Bike ran great ... but ... three times over the weekend, I grabbed the front brake and there was no pressure. This loss of pressure would happen only once and when I grabbed it quickly a second time, it was fine. But it happened three times and that is a little troubling. Any notion on why this might occur on my 2012 1200RT? Thanks for your input.

 

Wishing you a safe ride.

Morning Bob

There are a some possibilities on this one--

Possibly a failing master cylinder or failing master cylinder piston cup. Maybe some reason that the front master cylinder is taking air into the cylinder bore while riding.

Or, possibly something wrong inside, or with, the ABS controller itself.

Or, possibly the front brake rotors are kicking the front brake pads back into the calipers enough to need one cycle to extend them before braking can begin. (this could be due to a loose front wheel on the axle, or failing wheel bearings, (or something wrong at the front wheel area)

This is a serious condition & needs to be found & addressed quickly.

How far did you need to ride before the problem re-occurred & how far had you ridden since the previous pressure loss occurrence?

Any rough road riding just before the brake pressure loss?

Is the front brake rotor color normal or are they bluish/purple looking?

Good Morning DR,

I'll check everything you suggest this week. I was looking for a pattern but three data points over 700 miles is an insufficient sample. I happened once going into a corner (that was puckering) and twice just turning into the hotel and the gas station. It's just for a second, nothing and then normal. My inclination is the seal on the master cylinder but the infrequency is odd and the fact that I can't replicate the failure. My fear is that this is not testable, an error code would not come up with a scan. If I bring it to the dealer, they will have no choice but to start replacing components starting with the master cylinder I expect and proceed using the logic of elimination. I'm trying to think about what condition would allow something like this to act in an isolated rather than patterned way?

I agree, it's serious business. I replaced rear pads before I left but I'm thinking that my 2012 systems (as compared to my 03RT) is independent. Once should not have an effect on the other.

Take care.

Bob

A real light continuous pressure on the front brake lever may show a master cylinder cup that is failing.

The rubber gets old and does not always push out against the bore. Under normal or quick pressure it may work just fine.

Push ever so gently, as light as can be S L O W L Y add a little more pressure (travel) and see if the lever moves. If you can get it to move without building pressure, its the master cylinder. This should take a minute or more with minimal pressure on the lever, almost none, Just enough to move the lever a fraction of an inch at a time.

I think I understand you have brakes on the second application?

Have you had the cover off the master cylinder and look in there? Do you see mud? If the fluid level proper?

Best of luck, I am interested in what you find.

David

Thanks David ... I'll give that a try. Stopped at my dealer today for a chat. The mechanic suggested that the first thing I do is bleed the breaks. He wonders if there is an air bubble in the system. Also suggested that I keep on kickstand and cock wheel as far as i can to the left so that front reservoir is as high as it could be and see if I can make this condition occur. Hmmmm!

Bob

Old thread I know. Just yesterday I experienced the very same issue as originally posted.  Wondering if any additional input regarding cause is available.  Brake flush was completed a few months ago and brake operation has been normal since.  Thought temp might play a role as it was cold soaked at about 40 degrees.  After a night in the garage (55 degrees) it occurred again.... very random.  While present for several handle pulls I noticed some fluid activity in the reservoir.  No codes set  2012 RT, 88k miles.

8 minutes ago, Craig G. said:

Old thread I know. Just yesterday I experienced the very same issue as originally posted.  Wondering if any additional input regarding cause is available.  Brake flush was completed a few months ago and brake operation has been normal since.  Thought temp might play a role as it was cold soaked at about 40 degrees.  After a night in the garage (55 degrees) it occurred again.... very random.  While present for several handle pulls I noticed some fluid activity in the reservoir.  No codes set  2012 RT, 88k miles.

Afternoon Craig G.

That activity in the master cylinder reservoir could be indicating the primary master cylinder piston cup is by-passing the fluid that it is supposed to compress. 

Or it could be a big air bubble in the system that migrates up into the master cylinder piston bore.

Did the lever have ANY resistance at all, or just free movement with no feel of any resistance?  

Top of the day. I now remember how I fixed it. All I did was a good brake bleed. It never happened again. However, I traded it for a 2018 a few months after the post but left a paper trail with the dealer about this situation to be a good citizen. Cheers.⁹

Okay....Thanks

On 1/15/2024 at 12:51 PM, dirtrider said:

Did the lever have ANY resistance at all, or just free movement with no feel of any resistanc?

I'll say no and yes, no resistance at all and yes, free movement with no feel of any resistance.  Not clear what the difference is between the two.

Action taken so far:

- Bled at master cylinder port several times with no observed air escape. Handle bar cranked to the right.

- Cycled through every GS911 brake system service function several times.

- Approx 50÷ handle pulls since with no repeats.  Will be doing brake checks at every opportunity until confidence returns.

Keep us informed please Craig.