Guys,
Cannot for the life of me get this front brake to bleed. Systems specs are-
Brembo master, new MotoMaster braided line and MotoMaster MXC caliper.
I’ve tried all the tricks, regular manual bleed, vac bleed, reverse bleed, bleed at the banjos, remove master from bars, remove caliper and hang over head, turn the bars lock to lock, tapped the line, tie down lever over night, push caliper back in manually, etc. I’ve even replaced the banjo bolts with traditional style bolts with two holes in them. Nothing is working, lever is soft enough to pinch fingers against the bars.
I swapped the master off another bike and same story, but the master on the bike now was able to get firm lever on the other bike. So I believe the master is functioning correctly, so not sure if air is trapped in caliper or what. I’ve run a whole quart through this thing with no success.
Try moving the entire brake system to the other bike. I say this because maybe the caliper mount is bent or the rotor is bent... something that is holding the pads apart or holding the caliper cockeyed and causing the excess takeup.
It sounds like you've tried most of the tricks already. Have you tried this one? I've gotten quite a few hard to bleed issues resolved this way.
Everything is new, rotor, caliper, carrier. Bike/forks only have like 7hrs and show no signs of any damage/impact.
Mighty Vac and master on the floor? I’ll go try it right now lol.
Couple tricks I have when I have trouble with this.
Ziptie or tie down around lever during transport. The vibration and jostling helps. Try riding it and then back bleed it. Nothing crazy, just the turn track or some easy trails. A little heat and movement might knock something out. It sounds like you some nook in there with an air pocket.
No real success with the master on the floor and caliper mounted. I moved a bunch of fluid with my air power vac, just kept the master full and let it pull fluid through. pushed caliper pistons back in and did some more. Even tried manual bleed after that with master still on floor.
Have the lever tied down now, again, see what happens in a few hours. Manual says to pressure bleed, I’m almost ready to cob up some diy pressure bleed thing here
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What levers do you run? I put a Rekluse on my FC450 and couldn't get the clutch to bleed. I called Rekluse and the first thing he asked was what levers. I have ASV levers and was told to put the stock lever back on and try. I got almost immediate bleed. Just an out there thought.
I do have an ASV on there, and have the adjustment all the way out for full travel. I put a stock lever on to see if it was a lever ratio thing and it felt the same.
I could swap it over and try bleeding with the stock lever but I’m not super optimistic.
With the lever tied down I can still turn the wheel by hand. I know the rotor and pads are new and not bed in, but this thing is weak.
Yeah, I would definitely try bleeding with the stock lever on, just to eliminate that variable. You should not need a power bleeder. If you do, something else is going on. Maybe the bleed nipple is not seating nice in the caliper?
I'll swap lever and try later. Bleeder seems to seat OK? I'm not sure if there's a bubble trapped in the caliper somewhere or what, might try taking it off and bleeding it in weird positions to try and get something out
If you have some pressure pull lever in and crack top banjo first to bleed then do bottom then go back to bleeder couple times
It's air that is trapped. Keep the brake caliper on bike, make sure you have a upwards going path for brake line all the way up to reservoir. You might have to pull it down in fork guard mount.
First you can bleed with reservoir on handlebar.
Having a transparent tube connected to caliper bleed bolt and going 30cm is good. Let the fluid just run through.
Make sure the incoming end of brake line to reservoir, doesn't point down anywhere.
Bleed then by flicking the brake lever with handlebar fully turned left and right, tapping on breakline. Just leave the caliper bleed bolt closed
When there is no more air coming, remove reservoir from handlebar and start moving it in different angles and height. Plenty of air will come out. Air is also trapped on both sides of reservoir bleed holes so need to have it turned in all directions at different points.
Still trying everything.
Put stock lever back on to see if it helps, didn't notice anything beyyer really.
Took caliper off mounting bracket and pumped pistons way out and back in a few times. One thing I did notice is the lower piston is slow behind the top when just free pumping it. I assume it's just because the fluid is hitting and filling that top piston bore first. When the pistons were out I rubbed a little brake fluid on them just to make sure they aren't just sticky.
After another 1/2 qt of fluid maybe, some minor improvement. I've been at it so long and squeezed this lever so many times I don't know what is what at this point.
Well I tried suspending the caliper up high above the master, then I lost the little bit of lever I had. So all signs are pointing to air, but I cannot for the life of me get it out. I tried bleeding it from above, both manually and with vacuum bleeder. Still no success, I’ve been at this for like a week lol
If your still not getting it time rebuild the master
Its air and you won't get it out by "bleeding" the normal way as I wrote above.
Basically stop bleeding by pushing new fluid.
To get it back to new feeling, there is only one way.
- Bleed anyway you want. Push fluid from bottom with syringe or normal from top with open/closebottom valve. When you think you are done and it does not improve anymore:
1. Make sure the upper end/mount for brake line (banjo bolt) is facing slightly downwards
2. Twist the reservoir so it is at its maximum highest point.
3. Pull the break line down in the fork guard mount and fix it there so you get a straighter line up at the reservoir
4. Bleed again by flicking the brake lever and tapping on the brake line. Also move the bars from fully left to fully right. Air will be trapped on both sides in the reservoir
5. Remove the reservoir from the bars and hold it higher. Move slowly in different angles. Air will come out slowly that is trapped.
6. Can take up to 30-40min to get all air out.
There is a lot of small pockets from the front number plate highest point to the reservoir fluid hole where air is trapped. Takes time to get it out.
I had to make a DIY pressure bleeder for my car. One of those cheap, pump up sprayers. I had to buy a new reservoir cap...drilled a hole...threaded in a barbed nipple. Pump the shit out of it and pray it works.
Lay the bike down on each side. It may dislodge the trapped air and allow it to pass through to the reservoir.
I've had luck with this in the past.
Same that happens if you tip over and lose some of that feeling. But just remove the reservoir and move it around while flickering the lever. I'm always surprised how much air hides in there 😄
UPDATE-
Nothing worked. Took everything apart, pistons out of caliper, ect. One of the pistons is much tighter than the other in the caliper. I measured them but they are both the same size 23.98mm-ish. Called Technical Touch as they are USA importer for MotoMaster. Tech wants me to reassemble and run in the caliper a bit.
Put everything back together and did the following-
Gravity bleed
Pump lever a few times
Draw a decent amount of fluid through system with vac bleeder.
Pumped lever and got so far the best lever to date. I've been flicking and teasing the lever and turning bars lock to lock and its not getting any better but not getting any worse.
Not sure if a sticky caliper seal is at fault or what.
Got it held down and I'll check it again in the AM.
Pit Row
Putting the master on the ground like that will trap air at the highest part of the brake line. Was there something wrong with the stock caliper? I might go back to that to see if the new caliper is the problem.
It's not really a method you'd use from the onset starting with an empty line/system. But in situations like this one (full system but proving hard to bleed) it can many times be the trick that works.
Need to remove the reservoir from handlebar also and flick the lever. Won't get everything out while it's on the bike.
I'm starting to suspect that sticky caliper piston you mentioned.
Hope you get it sorted out!!
I think so too.
After reassembly, it seems better. Has maintained lever and has not gotten any worse, best it’s felt yet. I keep using aees bleed method and holding down the lever.
Out of town for a few days so I’ll leave it strapped down while I’m gone. It’s light years better than it was so I actually might try riding it and getting some stuff moving and heat cycled.
I just went through all this on my fc250, the air was at the banjo bolt on the master. you would think that with all the bleeding it would have made it's way to the caliper, but no...
Try using a hand held massager on the line starting at bottom working your way up. This has worked for me to get that air pocket out I couldn't seem to get any other way.
Just to update this, I really do not believe it’s air at this point.
Ive held the lever down over night, durning transport, I’ve left it alone, it feels the same, no change. It’s hard to explain, but it feels like there is just too much lever travel resulting in a “soft” feeling. I really believe at this point it is the sticky seal on the caliper, but after a couple rides in it does not seem to be improving.
I might order a set of seals and replace them but for now I’m riding it hoping for improvement. This caliper came with the bike, and though I “paid” for it, I’d be pretty disappointed if I dropped the coin on it myself looking for an upgrade.
Its air, have you tried my steps?
If you pull the lever, is there at least some movement of the pistons? That would be consistent with air still trapped. If not it may be problem with the master cilinder. Tbh it should've been fixed after all that though. Reverse bleed with a syringe is really the best way to do it, if you put a little teflon on the threads of the bleeder screw that helps to have a better seal when flushing. Pushing the air up and out is better than trying to collect them at the bottom. Be sure to fully press in the pistons repeatedly and pump them out again cause it's an easy spot for air to be trapped. Remove the caliper and try to get the line in an angle without any bends
Tried dude, I want to believe lol
Do you have another bike standing around? You can bolt the banjo onto it's caliper and see if you get that bled and working properly. If so, there is still air in your caliper or it's leaking past the seals somehow, if not your master cylinder may have gone to shit. Worst case you have two bikes with air in the line, lol.
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