MV Agusta Forum banner

101 - 120 of 136 Posts

·
Registered
Joined
·
561 Posts
Update on my Dragster RR rear brake: since MV expert re-bleed last May: still perfect. It is holding through very hot weather and some hard use.
 

·
Registered
Joined
·
561 Posts
Good to hear mate. Was this based on S/B 189 rev1?
Honestly I don't know for sure. I do know my mechanic removed the brake assembly and patiently bled it while flipped upside down. He really knows these bikes. Earlier in the year I had another mechanic replace the rear brake cylinder and bleed: did not last very long.
 
  • Like
Reactions: Skintkarter

·
Registered
Joined
·
46 Posts
Honestly I don't know for sure. I do know my mechanic removed the brake assembly and patiently bled it while flipped upside down. He really knows these bikes. Earlier in the year I had another mechanic replace the rear brake cylinder and bleed: did not last very long.
Would be interesting to understand why the master cylinder was replaced.
 

·
Premium Member
Joined
·
174 Posts
I think it clearly show it's not the MC's fault. It's quite difficult to remove air completely from the system given it's lay out and geometry IMO. My unscientific theory is air gets trapped somewhere along the ABS system. And when it's activated and/or after some useage it gets back in the line somehow. I say this only after noticing my level going down (no leaks, not boiling away). Obviously in my case it was not bleed completely. Even though my pedal was firm. I've had no issues since.
 

·
Registered
Joined
·
46 Posts
I think it clearly show it's not the MC's fault. It's quite difficult to remove air completely from the system given it's lay out and geometry IMO. My unscientific theory is air gets trapped somewhere along the ABS system. And when it's activated and/or after some useage it gets back in the line somehow. I say this only after noticing my level going down (no leaks, not boiling away). Obviously in my case it was not bleed completely. Even though my pedal was firm. I've had no issues since.
A possibility that you had air trapped in the secondary side of the ABS unit - your symptoms would add up to that conclusion. Was your bike bled using SB 189 rev1? - so by a dealer in the last 2-3 months since the revised SB was released?

Incomplete bleeding does not explain the damage noted to our master cylinder. Again not the fault of the M/C, there is something else going on and the M/C is an innocent bystander.

After having the bike bled under SB 189.1 by the local service agent and the importer on 25th of June, bike was ridden a couple of times and the brake again began to soften. I was taking daily measures of the pedal travel and the pedal was able to be pumped back up from the first stroke by 10-12mm, indicating the presence of air. Probably 6 weeks after the bleed, with the pedal still slightly soft (although having stabilised at 10-12mm whilst the bike was parked up) we did a bunch of electrical tests around the M/C looking for any stray voltages. I also took the top off the reservoir to measure the fluid voltage and played around with the brake pedal to determine at what point the brake light switch operated. Nothing untoward was noted, other than the reservoir diaphragm was pulled down into the fluid slightly and the body of the reservoir appears slightly distorted - sunken on the outward side. Reassembled everything and left overnight. Lo and behold, when I went to measure the pedal travel the next day, the pedal had firmed up again and was not able to be pumped up.

Very strange.

Plan is to now ride the bike to see if it deteriorates under use.

Does anybody have a copy of S/B 189 rev 1?
 

·
Premium Member
Joined
·
174 Posts
I think yours is an isolated case regarding damage to MC. I don't see this across the board as an issue. Nor do I believe there is phantom voltage causing the pitting.
 

·
Registered
Joined
·
46 Posts
I think yours is an isolated case regarding damage to MC. I don't see this across the board as an issue. Nor do I believe there is phantom voltage causing the pitting.
Assume from your response that you are tied up with MV in some way? If our pitting (on a new M/C fitted under warranty 12 months ago) is not electrical in nature, then pray tell what is it?
 

·
Premium Member
Joined
·
174 Posts
"Our" pitting? You're the only one here claiming pitting that I've read. You're speculating. People have replaced MC's and still had issues. Clearly IMO the MC does not seem to be the culprit.
 

·
Registered
Joined
·
46 Posts
Of course I'm fucking speculating - nobody else has an answer or seems to be digging. What is your answer? Are you digging at your dealership? Has repeat bleeding resolved all your warranty cases?

Our new master cylinder is significantly pitted after being replaced 12 months ago under warranty (due to 'corrosion/erosion'). Repeated bleeding to date has not been efficacious. If I can unravel the damage to our master cylinder, it may be a clue for other people (and MV who I'm in direct contact with) with this ongoing serious safety issue, who, call me a cynic, would seem to be being strung along with bleeding until the expiration of the warranty.

Disclosure - I am the parent of the owner of this premium machine, proudly bought new, but in 18 months of ownership, he has not had use of the machine for over 5 months and for the balance of that time, it's seldom had a rear brake that would pass local safety inspections. The original dealer has gone and the new dealer walked away from the agency after just 6 months. We have no dealer now in the North Island of New Zealand and I am trying to get to the bottom of the issue on behalf of several owners in NZ and elsewhere.

Should anybody else feel they are being given the run around over this issue and wish to discuss outside of a public forum, feel free to send me a private facebook message at Richard Pykett.

I won't be wasting my time on here in future.
 

·
Registered
Joined
·
353 Posts
Calm down. You are doing good job by investigating something most of us have experienced, and some of us (like me), have no idea what to do but trust our service and repeat bleeding process every few months. I had my rear brake bleeded 7-8 times in last 5 years. We added heat protection to the M/C and tried different brake fluid (racing). Then I tried new service location and they’ve done a much better job. I use my rear brake very rare now because I forget I still have it but it’s been 1 year since they bled it last time and it is still holding and has not dropped all the way down. It’s not as strong as it was last year but I see an improvement. I will take my bike to a scheduled service later this month and ask my service guy how did he improve the bleeding and service last time because for me it was an improvement.


Sent from my iPhone using Tapatalk
 

·
Super Moderator
Joined
·
22,622 Posts
Discussion Starter #113
@Skintkarter: There is no need to become unhinged at someone for a differing opinion. Please keep it civil.

We have had discussions about the lack of voltage present, the very low probability that brake fluid passes current, and the fairly large number of bikes with this issue.

Even galvanic corrosion is unlikely as brake fluid is poor electrolyte, and, as you know, you need dissimilar metal and an electrolyte between them to create a galvanic cell.

There are others of us also working quietly behind the scenes to see what the issue may be.

Did you inspect the new rear master for pitting before installation to look for pitting left in the manufacturing priocess?
 
  • Like
Reactions: Lucaoscar

·
Registered
Joined
·
494 Posts
The rear pedal on my bike is still as it was, after installing a direct DIY pipe from the master to the caliper.
The ABS system does not seem to care that the rear circuit is abandoned...

On the other hand; the low fuel circuit warning is becoming more frequent. I know that's another thread.
 

·
Registered
Joined
·
987 Posts
My Peneth worth;

Dragster MY19 On road March 2019, currently 1500miles.

Two months ago lost rear brake, totally. Carried out 2017 MV bulletin, resulting in good rear brake.
Two weeks ago, bad rear brake. Bled again (lots of air) and have good rear brake again.

The reason for repot, is that on bleeding the line from the master cylinder to the ABS unit, I had black fluid coming out from the 'cracked' nut on the ABS unit. Did not get the black fluid from the calliper side of the ABS unit.

Possibly rubber disintegrating in the master cylinder or ABS unit?
 

·
Administrator
Joined
·
20,363 Posts
Not much rubber inside the ABS unit....and those things are tested to live forever due to the massive liability concerns. That was likely just rotten fluid you had never gotten out off the system previously.

ABS systems can be very difficult to bleed. Helps to have software that can "cycle" the pump.
 
  • Like
Reactions: Teeps

·
Registered
Joined
·
494 Posts
ABS systems can be very difficult to bleed. Helps to have software that can "cycle" the pump.
Agree.
MV's scan tool does not have the ability to exercise the ABS pump and valves. Making the operation even more of a crap shoot.

The black fluid report is troubling and may fit with the other guy complaining of pitting in the rear master cylinder.

I still think there is an internal problem in the ABS unit allowing air to ingress. But... what do I know?
 

·
Registered
Joined
·
374 Posts
Not much rubber inside the ABS unit....and those things are tested to live forever due to the massive liability concerns. That was likely just rotten fluid you had never gotten out off the system previously.
On an MY19 bike? The fluid must have been in there less than two years. What would cause it to go rotten?
 

·
Super Moderator
Joined
·
22,622 Posts
Discussion Starter #119
Two years is a long time.
 
101 - 120 of 136 Posts
Top