Evening all, For about the fifth time now, I’ve lost pressure on my rear brake on my 1200R Monster. It’s been bled by my dealer 3 times, by me twice and generally holds pressure on but every so often it just goes to sh*t and the pedal travels about two inches and won’t lock the wheel. Now I know rear brakes are not really a strong point on Dukes but this is getting silly. So today I tried again,usually tricks of calliper off and turned so the bleed nipple is up,used a vacuum system etc. and still naff all pressure. It was working fine a week ago which leads me to think that some isn’t right. Nothing is leaking but a sh*t load of air is getting in and apparently quite suddenly Given the cylinder is probably common to multi’s, pani’s etc., has anyone had a master cylinder fail or be defective? TIA Ped
Sorry to revive an old thread here but I am too in the same boat as you. I am considering replacing my rear master as well. I can seem to find any aftermarket alternatives at the moment but the OEM replacement is cheap enough I can throw one in and try it. Did you ever have any long term solution for yours?
Use a high boiling point fluid .. proximity to the exhaust / cat gets it hot I have a perfect rear brake on my MTS . Currently using ATE Super Racing Blue fluid , but others are available
A few Supersport 939 (same brake set up) owners in the US have reported the same problems and similarly heat from the cat was been said to be the cause. Some have had master cylinders replaced under warranty which seemed to fix it. Others have changed to a high boiling point fluid which also seemed to fix it. I'd try a higher spec fluid first.
Castrol SRF high temp fluid already flushed through it. The cat was removed at 600 miles when the termi system was installed. Was great when I put it away for the season. It went limp just from sitting a few months so I can confirm heat is not the issue in my circumstance.
There have recently been a few similar reports. Bike was laid up for winter, no rear brake on the spring. I haven't experienced this so I'm not going to guess.
I can pump the rear pedal and observe bubbles in the reservoir rising. Then let it sit for a day and come back and do the same thing and see even more bubbles. Based on this it seems to me a faulty rear master. It’s cheap enough to just toss one in. I was hoping @Monsterped could chime in on his experience, wether it be a solution or just living with it. Either way I’ll update with my findings after I replace it.
Forgotten about this thread! when I took it for service in October 19, Moto Radipo spent over an hour bleeding the rear brake, got a lot of air out, using a vacuum system. Didn’t ride it again until about 6 weeks ago due to sh*t weather and the brake wasn’t great but over last summer I found triggering the rear abs seemed to keep it at a reasonable level - the abs pump is self bleeding I understand. Only managed one more ride before lock down and it’s spongy again so I’ll bleed it again with some high temp fluid (no cat on mine). I’m not a big user of the rear brake so I’ve never worried about it too much but it needs sorting. I think I’ll stump up for some of these to make life easier http://www.stahlbus.com/products/en/bleeding-system/index.php still tempted to change the rear master cylinder Ped
Does the fault perhaps lie in the ABS pump? Perhaps a faulty seal, allowing air back into the system? I really don't know, but it's what occurred to me when I read the above
@Monsterped those bleeder valves you posted look like a fantastic product. Definitely would make the process easier. I just ordered a new rear master and new crush washers for the banjo bolt. I imagine it’ll be a week or two before I receive the parts but I’ll update the thread when I get things replaced.
It’s been a while but I finally got the parts yesterday and finished the install a couple hours ago. New rear master, crush washers for the banjo and a bottle of motul rbf. Replacement was very easy. Bleeding was a pain but after removing the plastic hose holder shroud I had enough slack on the hose to remove the caliper from the left side of the bike then move it in front of the rear wheel around to the right side of the bike and I put it on top of the rotor with the bleeder facing straight up. I now have a perfect, stiff, functioning rear brake pedal. Hopefully it stays that way for a while and I’ll update this thread accordingly.
Well I’ve stumped up for a Stahlbus bleed kit ( arrived yesterday, nice quality) and I’ve ordered a new rear master cylinder courtesy of Moto Rapido and some Motul RBF fluid. I ran the bike up on Sunday, a few miles down the road and the rear brake went to nothing again. I reckon it’s been bled about 5-6 times in three years, probably should has raised it as a warranty issue but I’m not a big user of the rear brake so kinda let it slide. Hopefully the new bits will sort it Ped
I could not live with that. Will this be the new plastic tank fiasco? I love my bike and can accept a few quirks. But with the brakes? No thank you. 2014 M1200S I love my rear brake and use it often. Adds stability etc etc It is on the bike and should work. I find myself often braking hard with both brakes. I have felt the ABS pulse for the rear but never the front. My question is... Is it Ducati? Or Brembo? at fault? Rex
update time stumped up for a new master cylinder and swapped it over and also fitted the Stalhbus nipple, low and behold I have a decent rear brake again, not ridden it yet (prob tomorrow) but the pedal has remained firm for a few days (normally goes a little mushy in a week). but... omg, how flipping good was the new bleed nipple! System was bone dry, undo bleed nipple 1.5 turns to fully open the ball valve and use a vacuum pump to fill the system, took about two mins, close the nipple fully, pedal felt quite good. Onto “bleeding” it, open it half a turn so the ball valve is in play, pumped through a couple of reservoirs of fluid, close valve, pedal good and firm. Chuffing marvellous!! I pulled the old cylinder apart to see if there was anything obvious wrong with it but nothing other than some uneven wear in the bore from the naked eye. I still think it was letting air in, perhaps via the reservoir connection but not sure.
I envy the bleed nipple ! I didnt go that route but I am pleased to say that now two weeks after replacing the master and bleeding I still have a stiff pedal!
I had a very similar issue with a Guzzi a couple of years ago, made worse with the linked brake system. Eventually, I de-linked the brakes to try and get rid of the problem. Nothing seemed to fix the rear brake issue until I realised that the replacement bleed nipples I had bought, specifically for the make and model of bike, had a completely different chamfer profile. I ordered another set, a different profile again! And it was different to the other two sets of bleeders I already had! It took four attempts to get the right ones. If you have had replacement bleed nipples, it may be worth checking that the bleed nipple seats fully into its conical home when you tighten it down in the caliper, or it may well be bleeding air into your system.
Moto Rapido have had my girlfriends Monster 821 so many times for this problem. The bike is now 2 years old and still has a rear brake that needs bleeding every month. They have changed the caliper, no different, and have claimed to have changed the master cylinder, no difference. Trouble is that there seems to be nobody at the dealer who can do any thinking, they just change parts and hope for the best. Has cost her a fortune getting the bike to the dealer and back under warranty as they charge for getting the bike back home.
My 2012 multi suffers this and I've just had a word in my ear from the MOT tester. I've had to turn the caliper upside down to bleed it, lots of bubbles came out. This needs doing regularly, like twice a year minimum. Not sure how a closed system can get air in it. I never use the back brake unless hill starting, so it's not due to overuse and boiling up. Dealer said they all do it and no recall has been issued. Bit shit really. POA of a job to do, exhaust cans off, rear wheel off etc
