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The weird thing is that there is no evidence of etching inside the swept area of the system, but definite etching at one area. If you look at the piston, the front etched area is similar to arc strike when you lose your earth when tig welding - a series of small areas of spark erosion. Even has a slight curve as though the piston is tipping slightly. Need to get the multimeter out when I finished dealing with all of this social media...
 

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This is getting interesting. As a reminder of my B3 experience: a) bike brake ok for 1.5 years, then b) sudden total loss, plenty of fluid, c) had my Guzzi master mechanic diagnose-- he replaced faulty rear master cylinder and bled, d) brake lost pressure gradually over next two months, e) bike in for maintenance, had another bleed about a month ago--brake so far remains functional.
What fault did the mechanic observe in the master cylinder at c) above?
 

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What fault did the mechanic observe in the master cylinder at c) above?
Tony, excellent question: he said he had seen a lot of Brembo rear MC failures on various Moto Guzzi bikes thru the years. Checking system pressure they concluded the MC was likely cause. I don't have original part-- so I don't have a lot of information, sorry.
 

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Right... I've had someone reach out to me today who is a design engineer in the motorcycle industry and has been involved with the design of brake systems for a number of manufacturers. I can't name the person as they are still working in the industry.

He has pointed me back to the ABS unit as the likely source of both issues - 1) the galvanic corrosion and 2) the arcing between the piston and bore.

The two issues may be connected. The ABS unit has a large enough power feed to it and bizarre though it is, the damage I'm seeing is plausible.

I'm feeding my findings back to the importer and directly to MV, but predictably haven't had any acknowledgement.

What I now need to understand is if anybody has had an accident on one of the 3 cylinder ABS bikes, where brake performance was thought to be an issue.

Feel free to send me a PM if you want to discuss off forum.
 

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Right... I've had someone reach out to me today who is a design engineer in the motorcycle industry and has been involved with the design of brake systems for a number of manufacturers. I can't name the person as they are still working in the industry.

He has pointed me back to the ABS unit as the likely source of both issues - 1) the galvanic corrosion and 2) the arcing between the piston and bore.

The two issues may be connected. The ABS unit has a large enough power feed to it and bizarre though it is, the damage I'm seeing is plausible.

I'm feeding my findings back to the importer and directly to MV, but predictably haven't had any acknowledgement.

What I now need to understand is if anybody has had an accident on one of the 3 cylinder ABS bikes, where brake performance was thought to be an issue.

Feel free to send me a PM if you want to discuss off forum.
In that case, why would this only affect rear brake and not front brake?
I had discussion about rear brakes in the past with my dealer. He is quite experienced guy with our MV Agusta, and he had a F4 running in 24 hours of Le Mans in the past. He told me two things :
  1. the rear brake's position makes it is not possible to bleed it properly unless you unhook it from the swingarm (if you let it in position, there will be a small amount of air in the circuit you can't remove at the highest point of the caliper, and therefore, with the time, requires a new bleeding). The procedure for bleeding the rear brake have been updated by MV Agusta a few years ago to reflect this.
  2. the position of the brake pedal itself plays against the things: if you have it too low for your position, you won't get the pads in contact with the disk. I can tell myself that 1 centimeter difference makes a big difference on the breaking as I can feel ABS making its work since I move the pedal up.
As matter of facts, I know few people with F3, B3 (ABS or non ABS models) and myself with a TV with no issues at all with rear brakes and that for more than 10000 kilometers... That being said, I also know people who had issues of rear brake, having their dealer bleeding it, and having problems again later on, and that until they went to another dealer. I'm not saying it is always the case, but some dealers are taking their work lightly on some case: many bikes are delivered while kept in inventory for few months/year without the recalls requested by MV Agusta being done, and that maybe part of the problem...
 

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The rear brake has been bled multiple times as per the service bulletins available at the time - the last 4 days ago in my workshop by the local Importer and nearest Service Agent and videoed to send back to MV as proof of adherence to the new Service Bulletin.

Agree that there are similar bikes out there with no issues - but plenty with to greater or lesser degrees. Bleeding, as the only 'solution' offered by MV, is only a temporary solution.

Repositioning the lever won't achieve a bloody thing if you have no brake at all... Last week the brake could not be pumped up prior to bleeding.

The rear master cylinder has been replaced. The replacement basically has made no difference and now shows signs of electrical arc damage.

I can't explain why the front circuit is not affected as I don't intimately understand the inner workings of the ABS unit, but assume that the circuits are separate so that a catastrophic fault in one would not disable the other. Electricity takes the path of least resistance when going to ground. Perhaps a short or an earth problem in the ABS unit finds that the nearest ground is via the rear master cylinder. You would need to dismantle the ABS unit to check for evidence, but you can certainly see it on the rear master cylinder piston.
 

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Tracking this as I had the rear brake go out today while riding my wife’s 2018 Dragster RR. Only 400mi on it. 30 mins into a 45 minute ride, it just went totally dead.
 

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Tracking this as I had the rear brake go out today while riding my wife’s 2018 Dragster RR. Only 400mi on it. 30 mins into a 45 minute ride, it just went totally dead.
Crikey mate! That is exactly what I feared would happen with this issue... When you get it looked at by the dealer, please get them to pull the rear master cylinder to inspect rather than just blindly bleeding the brakes. Please have them call you when they have it apart so you can photograph any damage/marking of the components. Get the best hi-res photos that you can - two people and holding a light up the M/C bore from below. Zoom as much as you can. Keen to see if you have similar damage to us. If you can, please grab a short video of the brake pedal action before it gets worked on. Thanks.
 

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Unfortunately there won’t be any taking this thing to a dealer as it’s a 4 hour drive.... EACH WAY! That’s why I didn’t want this thing. It’s my wife’s bike though and she had to have it.

I did bleed the brake out today though and it’s working again, if that tells you anything.
Crikey mate! That is exactly what I feared would happen with this issue... When you get it looked at by the dealer, please get them to pull the rear master cylinder to inspect rather than just blindly bleeding the brakes. Please have them call you when they have it apart so you can photograph any damage/marking of the components. Get the best hi-res photos that you can - two people and holding a light up the M/C bore from below. Zoom as much as you can. Keen to see if you have similar damage to us. If you can, please grab a short video of the brake pedal action before it gets worked on. Thanks.
 

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I did bleed the brake out today though and it’s working again, if that tells you anything.
Bugger, it would have been useful to understand the condition of the master cylinder bore to see if you have the same issue going on that we have. If you had a total and sudden loss of brakes, then can only assume that something more is going on.

Please if anybody else is investigating this problem, either at a dealer or at home, please pull the master cylinder to verify the condition of the bore and piston. Please take photos and post on here so that we can all learn and ultimately get MV to step up with a permanent fix.
 

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Mines going into the dealer in a couple of weeks for the rear brake that's also now useless on my Dragster RR 2018. I'm making a note of the comments and what people have tried so far, I will see if I can get a picture also when they take it to pieces...MV really should ' I feel ' step up and sort this as so many of us are having the same issues :(
 

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Mines going into the dealer in a couple of weeks for the rear brake that's also now useless on my Dragster RR 2018. I'm making a note of the comments and what people have tried so far, I will see if I can get a picture also when they take it to pieces...MV really should ' I feel ' step up and sort this as so many of us are having the same issues :(
Agreed mate. Show them the pictures of the internals of our M/C before they start. Offer to pay to have the M/C removed and stripped to make sure. If you would like copies of the Hi-Res images from our bike, just send me a PM and I'll respond. Had the same story from another rider this afternoon here in NZ - bike was bled a month ago according to the new SB and brake has completely gone already just from sitting. His is a 2018 Euro 4 Brutale 800 RR. It's only by building a photographic case in my view that we will force them to sort.

On another tack on this, I'm trying to speak with somebody at Nissin Ohio to see if they will comment on my M/C photos, but I'm really struggling to find an email address. Bloody anonymous Corporates... Does anybody have an email address for one of the US facilities? At the end of the day, their master cylinder is being blamed, but my theory is that the issue is elsewhere.
 
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