2021 RE 650. report card. NGC

[sidecarnutz]

My 2021 RE650 GT finally had its first issue last week. For almost a year and a half it has been downright Honda like. Huge change from the older 2003 RE500 Bullet I used to have.
Over a couple week period the rear master cylinder gradually quit working. I kept having to press that rear brake pedal down further to get pressure to build. Then it got soft enough that it no longer worked.
Its an ABS system, so I thought it may need a trip to the dealer to fix. They were kind enough to give me an appointment just a few days out. Then I put it up on my maintenance stand and did a simple vac assisted bleed on the rear system. That cleared the issue right up! No different from bleeding a Brembo on all the Guzzi's I have owned over the decades. It did suck air past the bleeder fitting threads and I got a glob of air out as the vac tank sucked the fluid thru.
I know from RE forums that a handful of us have had this issue. And all were cleared up with a bleeding. But the mystery to me is how did it wind up sucking air into itself to begin with? Anyone here ever see this issue before? In my 42 years on street bikes, it was a first for me.
I did contact the dealer to cancel the appointment and thanked them for their time. A week later the rear pedal is still rock solid. The bike comes with SS brake lines, so brake feel is very good IMO.

It is an ABS system, but the rear components look like they came straight off an old Guzzi EV. Brembo copies made in India. I consider that a good thing as I have great experience with Brembo over the years.
There was no change the rear MC level. 3/4 full. NO weeps or loose connections to air to get in.

[fotoguzzi]

Over time the fluid got moisture in it then the brake heated up and boiled the water leaving air? Wild guess.

[sidecarnutz]

Over time the fluid got moisture in it then the brake heated up and boiled the water leaving air? Wild guess.

Thank you. Fluid was still clear. 17 month old bike.

[9fingers]

The brakes ARE Brembo....sort of. Royal Enfileld uses Bye Bre..........think that is the name.......a division of Brembo.
Scott

[kingoffleece]

Check the rubber diaphragm under the rear "urine sample" cup.  I've seen them slightly tear just because............ .........

[lucky phil]

Check the rubber diaphragm under the rear "urine sample" cup.  I've seen them slightly tear just because............ .........

Some modern cap seals actually have a "slit" in them from new> I can tell you why if your interested.

Phil

[kingoffleece]

I;m aware.  Was just keeping it simple.  Not all have a slit IME.

[DesertPilot]

I had the same thing happen on my old Tiger 800.  Rear brake got weak, no drop in fluid level, no sign of leaks, air in the system, problem cleared up after bleeding a few cc's of brake fluid -- about 1/3 of the reservoir -- from the system without any need to take it to the shop or fool around with the ABS.  I never did figure out how the air got in, and I never had the problem again.

Now, years later, I realize that I never took a close look at the ABS servo, which lived in that unknown land between the master cylinder and the rear caliper, I believe had its own bleed valve, and was hidden from view... somewhere...  How is the ABS set up on the RE?

[sidecarnutz]

Rubber diaphragm on mine was fine.

On the RE 650 the ABS module is up under the tank. I had to take it loose from the mounts and raise it 1/2" to get the valve cover out to do the break in valve service.

[lucky phil]

I;m aware.  Was just keeping it simple.  Not all have a slit IME.

It's the 21st century, there is no "simple"
I'm also aware, that's why I used the word "some"
The post was more for the benefit of all readers, not specifically aimed at you. Quoting your post was just my link for the purpose of distributing more knowledge.
Phil

[lucky phil]

Rubber diaphragm on mine was fine.

On the RE 650 the ABS module is up under the tank. I had to take it loose from the mounts and raise it 1/2" to get the valve cover out to do the break in valve service.

Won't be this. It's one of those mysteries like why does my DD car use 300ml of coolant every 15,000klm service? No visible external leaks, no internal leak symptoms . I have a theory but can't do the science. Fotoguzzis theory sounds plausible but unless your a "rear brake dragger" I doubt it would ever get the fluid hot enough. 

Phil

[kingoffleece]

Yep.  I got that.  We're good-didn't mean it to sound otherwise.

[fatbob]

My ‘07 Norge does the same.   Needs an occasional bleed.   My ‘13 BMW R1200GS did the same too.   Just part of the game.   

[sidecarnutz]

I'm hoping that if I go to annual bleeds like I used to always do to my bikes, I won't see the issue again.

My foot on that side turns out away from the pedal. So I know I am not dragging it.

I appreciate the intelligent discussion on this folks! Thank you!

[lucky phil]

On the subject of brake fluid check the water quantity of the fluid before you leave the store. I use one of those $12 electronic pen testers and I've check the Cal on them and they are accurate. I had to change the fluid on my DD car with my pressure bleeder and as the new fluid was the same colour as the original I kept testing the moisture level as I bled the rear calliper but it wouldn't go below 1.5%. Then I checked the new fluid I'd just bought, yep 1.5% straight out of the sealed bottle. I had 500ml of 10 year old fluid on the shelf and cracked it open and tested it, and zero. Next time I buy brake fluid I'm testing it at the front counter before I pay for it.

Phil