Not a Ducati. Actually a 2005 triumph speed triple. trying to help a mate out who brought the bike with a sticky front master cylinder piston. I’ve stuck a rebuild kit in it, primed the lines, made sure pistons in callipers are free, clean & pushed back. Just won’t bleed. No lever at all. No leaks anywhere. Tried everything ( I’ve done this hundreds of times) even made sure nipples on calipers are sealed so when cracked off don’t draw air in. Took callipers off & move around in case trapped air. Nothing. Cracked top banjo off as no top nipple. I’m beginning to think the master is letting by, but can’t see how it can with new kit in. Anything I’ve forgotten. I’ve even tried zip tying lever up over night.
I don’t know as I’ve never owned one but does the master cylinder have a bleed nipple. I missed this once on my 04 R1 when I was bleeding it and it was easier once I bleed that first
No. As said above. No bleed nipple on the master cylinder but by cracking off the top banjo it will do the same if any air is trapped.
I had a similar problem once when fitting new HEL lines to an M900, just couldn’t get the lever to pump fluid down, got there in the end though. I can suggest 2 approaches. 1. Reverse bleeding ie push fluid up to the master from a caliper bleed nipple. 2. disconnect the banjo at the m/c pump the lever, put your finger over the disconnected connection to stop air being sucked back into the m/c before releasing the lever, and repeat until your sure fluid is coming out of the m/c. Reconnect the line. Repeat at the next joint and again at a caliper until you identify where the ‘blockage’ is. Eventually you’ll get fluid & air coming out of the caliper bleed nipple then it’s bleed air as normal. I’m guessing despite your best efforts (and this was my issue) the m/c isn’t fully primed.
Makes sense about the master cylinder. But correct me if I’m wrong. Surly if the mc isn’t fully primed then level of the fluid would drop very slowly when being bled. I’ve gone through so much fluid surly the mc is pumping as it should. Will give it a go tomorrow tho
Get a big syringe with a bit of pipe on it and pull it through from the caliper bleed nipple or just suck on the pipe to pull it through.
I always use one of them hand vacuum pumps when priming/bleeding the system. So good and never looked back.
I’ve tried the vacuum pump but to no avail. Fluid is coming through at the callipers as it normally would with no visible air bubbles. Must say the back bleeding with a syringe is the only thing I haven’t tried yet, mainly because with the vacuum pump I’ve never had to
That’s correct and perhaps I misinterpreted your opening post. So fluid is coming through when you pump the brake lever, no air bubbles present in it, but when you close the bleed nipple and pull the brake lever back it goes all the way to the bar with zero pressure build up. Does the bike have ABS ?
Like I say. Had bikes all my life & do all my own maintenance. Yes you’re 100% correct. The fronts are normally a breeze & it’s the rears that are the nightmare. I’m at the stage where I’ve done everything in my knowledge to no avail lol. Crying for help now.
It’s looking more and more as though the fault lies within the replacement m/c piston. Perhaps a tiny hairline split or a nick in one of the seal skirts or a less than perfect (due to corrosion & pitting) bore which is small enough to not matter when just pushing fluid through the lines but large enough to prevent a 100% seal when the pressure builds. Assuming the rebuild kit to have been ok what was the bore of the m/c like?
Bore seemed good during strip & install of new kit. Obviously cleaned & blasted with airline. I’ve had the top banjo off again this morning to check mc is building pressure by blocking with thumb etc & seems to build good pressure to the extent it shoots out when I release it. So to me that part is good to go. Now going to do the same with banjo’s on callipers to narrow that down.
So good pressure at banjos to callipers too. No leaks on callipers. Think it’s time to give up & pass it back
Where’s the bleed nipple on the callipers in relation to the banjo and fluid in? Is it possible there’s air trapped behind a calliper piston yet when you bleed the caliper the fluid is flowing almost directly from the feed banjo to the bleed nipple? I know you’ve been there loads of times already but perhaps if the calipers were removed (again) but left connected to the lines, pistons pulled out, fluid poured into the caliper, bleed nipple opened, pistons pushed back in until fluid is squeezed out of the bleed nipple, bleed nipple closed, then bleed them as per normal. Just a suggestion and, as I’m not familiar with the calipers on the Triumph, it may not even be physically possible, but you never know.
If there's as much fluid in the system as you say, and no leaks, then fluid must be getting past the piston. Is the piston/seal definitely the right size for the MC? Has the MC perhaps been changed in the past, so is not the OEM spec? Seems unlikely to be a coincidence that this started as a MC issue. I'd want to try a different MC next.
Sounds more in keeping with the bleeding thread? My Sons rear calliper on his Aprilia was a bleeding nightmare, resorted to buying a vacuum bleeding kit to successfully bleed.
Is it an aftermarket rebuild kit? I tried an All Balls kit once on a KDX200 and it turned out to be all balls. I shoved the original guts back in and it bled up straight away.
