Weak front brake and no pressure build up

[Lbrown311]

I just bled the brakes and have no air in the lines, but the lever WILL pull all the way to the handlebar with almost no resistance, and the M/C sounds really spongy inside. It is a new 16mm bore M/C from Mikes XS. I can see action in the calipers, but I don't feel any pressure build up when I pull the lever with the bleeders closed. Are these susceptible to the plunger undoing itself like the old M/C's or is there an air leak somewhere. I reused the crush washers from the calipers but the M/C has new ones. Doesn't feel like it would stop me rolling out of the driveway. Haven't really checked for bad/cracked lines. I will check that tomorrow. As for now I will hope for some responses and get these damn things working. Maybe I should bungy it over night and see what happens. Yep....doin it.

[petejw]

hi Lbrown311,

did u bleed the master cylinder?
crack the banjo bolt at the m/c and check
for any air, just be careful of any spilt fluid on
painted surfaces.
also check the levers free play?

[yamahansolo]

Hopefully you didn't do like me. I bled them too hard and flipped the rubbercup inside out.... I had to take the MC apart and you could tell it was flipped around. Symptoms werethe brake piston went in and wouldn't cone back out. Your supposed to use a board or something while bleeding it. Look in the brakes section under maintain or repairs ..

[Shacknasty]

Solo's probably on the $ here. If you squeezed the lever all the way to the barduring bleeding, then you will probably need to disassemble yer m/c.

Spend a couple pennies and buy new crush washers. Or not. They're just brakes.

[Lbrown311]

I did bleed the master, and I have the lever adjustment screw tightened all the way so there is no play thinking that would help, but it didn't. I see no leaks, just checked. Pressure definately doesn't build up until it gets close to the bar, so maybe there is an air bubble at the very top. Maybe just need to be a little more patient and spend some more time tomorrow working on it. Might take awhile to work out all the air. There is definately action at the calipers but it is making a spongy squishy sound in the master. Not sure what that is...could be the plunger on the cylinder piston... I cleaned everything already, including calipers and the cylinder, like I said is new, so there might just still be air in the system somewhere.

[old_chopper]

It can be a bear to get all the air bubbles out. Bubbles normally rise and yet we're trying to push them down out the calipers. I found that quick 3/4 strokes of the lever did a good job of getting pressure built up instead of bottoming out the lever each time.
I cheated on the rear and pressurized the m/c with air pressure then opened the bleeder. I have a different cap than most to allow for a remote reservoir.

[DGXSER]

Sounds like you still have some air in the system.

A little hint on bleeding the brakes I learned form some of the great minds on here, after you finish bleeding, put a spacer of about 3/4" on the handle bar, and pull the brake lever in to that spacer. Now put a bungee or similar around the brake lever to hold it in this potition, and turn your bars so the MC is up good and high. Now go inside and get a good nights rest. In the morning ( or some hours later anyway) release the bungee and you may find your air is gone.

That has worked for me on a couple of occasions.

[yamahansolo]

I did the bungees thing with mine and spent about 2 days bleeding and rebleeding. Mine would move the calipers a smidgen... and the little piston would move just a touch so the symptoms you just described are verbatim to what mine where. No amount of bleeding will work because the little rubber part is inside out.
Ill bet you 100 bucks in play money... I even put a clamp on the caliper cylinder and tried pumping... I got excited because it pumped up the MC piston... then I went for a slow ride and within a few mins the MC was almost deflated again... you can look at the pictures on mikesxs.com to see what it looks like mine was inside out.once I fixed it they worked awesome.

[Lbrown311]

I will check it out. It defiantely sounds like something is off in there. It is way to noisy for a brand new MC. Hopefully all goes well and I have front brakes today.

[Lbrown311]

So I took the MC off, and realized I didn't have the appropriate snap ring pliers and I just broke mine the day before(piece of junk, used it twice before it broke). So I just put it back on and got down to business. Used the rapid 3/4 stroke until I worked out the majority of the bubbles and FINALLY got pressure. They now stop the bike like they should. Rear brakes are fully operational as well now. I am a Carb sync and a tune away from riding again! Can't wait. I will probably have some more questions as the days go bye Thanks for the help. Can't wait to see what all my hard work has created.

[jwhughes3]

riding helps

When I did mine I bled till I couldn't pull lever back to the bar, but still not as hard as I liked. Figured it was the 16mm MC I put on. I bungeed it overnight and didn't notice a difference, but after a few rides it firmed up more. Just needed time for microbubbles to migrate to the MC.

Good job on sticking with it.

And always buy the best tools you can afford you won't be sorry. Tip - shop at Pawn Shops for big brand name tools like MAC, SnapOn, Proto, etc. I bought alot of tools very inexpensively over the years watching for deals. Craftsman is also a deal on hand tools like your pliers with free lifetime replacement.

John

[James England]

I've done my front brake 3 times in the last 3 months, due to taking bits off and renewing them. Also the rear brake because of a leaking caliper seal. I've encountered the no-pressure problem every time and always use the 'fast-jiggle' technique. Rapidly pull in the brake lever about 10 times but only pull it in very little (5mm), then pull the lever right in and hold it as you undo the bleed nipple. Repeat. After a few goes, you get slight pressure, then it increases rapidly as you repeat the process.

[fredintoon]

- - - It is a new 16mm bore M/C from Mikes XS. - - -

Hi Lance,
there's the problem. The m/c stock bore is 11/16" and 16mm is ~5/8"; that is, it's ~1/16" smaller. As the all important m/c to caliper ratio is determined by the difference in area rather than in diameter that 1/16" difference is a lot more than it looks to be.
OK, you can get away with it and it does make for a nicer feel at the cost of more lever travel but you need to get ALL the air out AND switch to s/st brake lines or she'll sponge right up on you.