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It's not a matter of time. It's more a matter of use and distance ridden.
AND time....moisture absorbed while just sitting. Especially in hot and humid environments.
 

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AND time....moisture absorbed while just sitting. Especially in hot and humid environments.
My rear brakes fails, without any use. Unfortunately we are talking days/weeks, rather than months/years. Not particularly hot or humid here though.
 

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My rear brakes fails, without any use. Unfortunately we are talking days/weeks, rather than months/years. Not particularly hot or humid here though.
That's air in the system, not fluid degradation..... the problem is "how is it getting there?" and "how do you get it all out easily?"...questions not answered.
 

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It's not a matter of time. It's more a matter of use and distance ridden.
AND time....moisture absorbed while just sitting. Especially in hot and humid environments.
My bike has about 7200 miles. Bought new Jan 2018.
Pedal was low at delivery but I didn't notice, as I rarely use the rear brake.
I bled the brakes per the service bulletin several times for the next 2 years.
After bleeding within 6 months or less the pedal was low again (2000 miles or less.)

Early this year I built a DIY line and bypassed the ABS. It's been fine so far this year; however I have not put that many miles on the bike because of the wuhan flu and medical reasons.
 

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@Teeps , I am convinced the ABS system is the cause of so much aggravation on the MV 3 cylinder bike rear brakes, although I can't explain how since many other brands and bikes have a similar system (components and design), and the front brakes use the same pump/module with some long convoluted routing hoses.

Your eliminating it with good result seems to uphold this suspicion.
I wonder if any of the 4 cylinder ABS bikes have had similar issues??

Odd that MV reputedly doesn't have ABS test cycles in the diagnostic software. Most manufacturers do.
I think I'll chat with my local MV dealer about this and get his insight.
 

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@Teeps , I am convinced the ABS system is the cause of so much aggravation on the MV 3 cylinder bike rear brakes, although I can't explain how since many other brands and bikes have a similar system (components and design), and the front brakes use the same pump/module with some long convoluted routing hoses.

Your eliminating it with good result seems to uphold this suspicion.
I wonder if any of the 4 cylinder ABS bikes have had similar issues??

Odd that MV reputedly doesn't have ABS test cycles in the diagnostic software. Most manufacturers do.
I think I'll chat with my local MV dealer about this and get his insight.
During my stint working for Honda (AHM) we had a similar problem that involved Accord models from 2003 to 2008.
Service Bulletin: 07-045
Dated: April 13, 2010
SYMPTOM: When you apply the brakes, the brake pedal travels lower and feels softer than normal.
PROBABLE CAUSE: The ABS/TCS or VSA modulator-control unit has leaked air into the brake system.
CORRECTIVE ACTION
Replace the ABS/TCS or VSA modulator-control unit (modulator assembly).

I believe the ABS unit on the TV has a similar problem.
RE: reoccurring air in the brake system.
 

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@Teeps Just not sure how air gets in there. I have disassembled (destructive unfortunately, no other way) several ABS modules. There ain't a lot to it... Regardless, air is getting in somewhere and the ABS unit is the only place I can imagine without fluid also getting out.
Here are a few pages from a Suzuki manual that have great diagrams of what is in that module and how it works. Not an MV manual, but all ABS system used on bikes work in similar ways.
On the ABS PDF diagram the "Solenoid Valve OUT" are the ones that help prevent the pulsing of the lever during operation present in early ABS systems. The reservoirs act like shock absorbers.
 

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@Teeps Just not sure how air gets in there. I have disassembled (destructive unfortunately, no other way) several ABS modules. There ain't a lot to it... Regardless, air is getting in somewhere and the ABS unit is the only place I can imagine without fluid also getting out.
Here are a few pages from a Suzuki manual that have great diagrams of what is in that module and how it works. Not an MV manual, but all ABS system used on bikes work in similar ways.
On the ABS PDF diagram the "Solenoid Valve OUT" are the ones that help prevent the pulsing of the lever during operation present in early ABS systems. The reservoirs act like shock absorbers.
At Honda I was not a subject matter expert of ABS (systems.)
And, my knowledge of ABS function is limited to what I had to learn for Honda autos, to do my job.

So I don't pretend to know the how or the why air might invade the rear brake circuit on our MV motos...
Only that in past experience IT can and does happen.
 

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Meanwhile the factory decided to install one bleeder on the 2020 models, it is interesting that only in the input line.

54DFC21F-36A8-46CE-83D1-5D10E0016C97.jpeg
 

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Looks like they are assuming that the problem is between Abs and MC.
I doubt they are assuming anything...I will wager there has been massive study done.
 
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That one (from master cylinder to ABS unit) is where I get the air and black substance from, so that concurs with my problem. Apart from the black substance :(
 
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