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**dbeardslee** · 04-01-2010, 07:15 AM

When you're bleeding your brakes the manual tells you not to pull the lever in too far as the little plunger seal can turn itself around backwards. It's recommended that you put a piece of 2 X 4 between the lever and the handlebar so you don't squeeze it too far. That being said, XS brakes are notoriously difficult to bleed - particularly when you are starting with a dry system. I've found a power bleeder to be very helpful.

**GARTHXS** · 04-01-2010, 08:36 AM

+1 on the mity vac, other wize it is a complete pita

**psycoreefer** · 04-01-2010, 09:04 AM

If you look back about a week ago I had a post about front brake problems, there are about a dozen tips for bleeding breaks in there. I was positive I didn't have any air in my brake lines, tried all the tricks, finally I gave up and went to bed, got up the next morning and pulled the lever about three times, now it gets nice and hard about 1/3 to 1/2 way to the bars. Not sure what changed, only thing I can figure is maybe there was a bubble some where in the middle of the lines and letting it sit let the bubble come back up to the master and "burb" when I pulled the lever the next morning.

I suppose another issue could be I worked the master so much that the air in it turned to a break fluid "foam" and thats why I couldn't get it out, and letting it sit let the bubble collect.

Anyways maybe take a brake and let it stew for a little bit, then come back to it when your fresh.

**Ken Talbot** · 04-01-2010, 09:24 AM

You have to remember that you're working with a reservoir of fluid sitting at the top of a long skinny system that starts off full of air. Every little nook and cranny around the pistons, every fitting, every banjo bolt, all of it full of air.

Then you start flushing fluid down this system with a small volume pump - the master cylinder.

Some of the air gets trapped by a wave of fluid and gets pushed out the bleeder screw. Lots of it manages to hide in all those nooks and crannies. When the fluid flow stops, some of the trapped air, now in smaller, dispersed bubbles, tries to rise through the thicker brake fluid. Then, you start pumping again, and the bubbles get pushed back down, but without a high enough, sustained flow, not enough to be pushed out the bleeders. Stop pumping, the bubbles start to rise again. And on, and on, and on.

Left alone, some of the trapped bubbles will rise all the way to the master cylinder, where the only way they can escape is through the spooge hole, and you know how small that is. Some are small enough they will still be stuck in the wee nooks and crannies until time, a bit of vibration, and the current caused by applying and releasing the brakes loosens them. The loosened bubbles still need to travel up and exit the spooge hole.

Sounds frustrating - yes. Sounds hopeless - no.

The mighty-vac works by giving you a large fluid flow through the system - larger enough to keep pushing any bubbles down and preventing them from floating up. When you're using a mighty-vac, the last thing you want to do is stop for a minute while you pump up the vacuum again in your collection jar. Without a mighty-vac, the bubbles will eventually dislodge, float up, and exit, but it will take time and patience.

**trbig** · 04-01-2010, 09:25 AM

I've got nothing usefull to add here.. I just popped in to stare at your avatar.

Tod

**psycoreefer** · 04-01-2010, 09:59 AM

Originally posted by Ken Talbot View Post

The mighty-vac works by giving you a large fluid flow through the system - larger enough to keep pushing any bubbles down and preventing them from floating up. When you're using a mighty-vac, the last thing you want to do is stop for a minute while you pump up the vacuum again in your collection jar. Without a mighty-vac, the bubbles will eventually dislodge, float up, and exit, but it will take time and patience.

I just have to add that I have a brake vacuum, its not a "mighty-vac" brand but its the same darn thing. I used it and still couldn't suck those bubbles down.

**ManitoulinLad** · 04-01-2010, 12:05 PM

Hey TrBig: I agree, I never miss one of his posts, I am sure he gets the most hits - Dan

**randy** · 04-01-2010, 12:41 PM

Originally posted by psycoreefer View Post

I just have to add that I have a brake vacuum, its not a "mighty-vac" brand but its the same darn thing. I used it and still couldn't suck those bubbles down.

I tried the same thing, but now my mighty-vac is stuck to the screen over Tom's avatar. Another -1 for mighty-vac

**DGXSER** · 04-01-2010, 01:05 PM

Best suggestion I have and I can tell you it works is to bleed them out the best you can, then take a bungee or string/rope and squeeze the handle to your brake lever about 2/3 in and tie it off there. Now walk away and come back tomorrow morning, or 4-5 hours later. Release it and see what you get. Re-bleed and repeat as needed.

This is a trick I believe Prom stated at one time. And I have used it more than twice and it works every time I use it.

**Larrym** · 04-01-2010, 02:41 PM

Bubbles and Bath-tub Etiquette

Sure, if there's air in a hydraulic line one way to get all the air out is to force the fluid through with sufficient speed and force to literally blast/dislodge every single air bubble from wherever it's "hiding" and shove it out an orifice. Doesn't matter whether it's done by massive/continuous pressure at the input or the same thing done by vacuum from the output side. It's quick/easy if you have the right pressure or vacuum device: brute force/turbulence and sheer flow-rate overcomes the helpless little air bubbles.

But bleeding the system without using the "brute force method" takes a little finessing. The MC can only deliver "pulses" of fluid with little if any pressure at first and not much flow per "stroke". I've found that going at the process "aggressively" like your mad at it just doesn't work: Full travel strokes done quickly followed by another one just like the one before.

I suspect that all that results from doing it this way is that the fluid pushes the air bubble down and by the next stroke the bubble has risen back up (That's what bubbles do in case you've ever farted in the bath tub and watched what happens...) to near where it was in the first place. The cycle repeats itself with the little air bubble effectively "bouncing in place" and the XS owner versus the Battling Bubbles ends up in a Mexican Stand-off.

That's largely due to the way air bubbles behave in a confined area like a narrow "tube" where they can use the sides of the "wall" as a grabbing/friction point. (They don't behave as if they were in the "free-and-clear" like in the easily reproduce-able/verify-able bathtub scenario...). Apparently, the combination of the bikes MC piston/stroke and the length/diameter is just about perfect to start and sustain this "Bubble Battle" much to the frustration of those without the brute-force bleeding equipment. Having man-hands with the usual upper body strength works against the owner in this case.

IMO the way to win this battle is to take advantage of the bubbles weak point: it's attachment to the inner walls. Smooth and slow strokes with the MC/plunger push the fluid through at just the right speed to break the bubbles grip between itself and the walls. After all, if the bubble is large enough to totally expand out far enough to touch the walls on all sides, the fluid has to get past the bubble by "leaking" past it along the sides. This disrupts the "hold" between it and wall and releases the bubble. Total release and it Pops up a bit while partial release means it will "crawl" up while still partially attached. Then the bubble has to do what it would normally do: be gently displaced upwards by the weight of the heavier brake fluid. Anything faster than this pushes the entire bubble downwards and on the recovery stroke of the MC the bubble has that window of opportunity to climb back up.

Only one way for the bubble to go after this: up-n-out.

If you just can't stop pumping the lever like Arnold Schwartzeneger then May I suggest that you do like XS11Lover did: give the task to teenager along with instructions to go slow while keeping the MC from running dry. Then walk away for an hour.

**Ken Talbot** · 04-01-2010, 10:39 PM

Hmmm, never thought of the bathtub f@rt bubble analogy before, but I love it!!! I'll have to remember this for next time this problem comes up.

**Larrym** · 04-01-2010, 10:56 PM

Bubbling and Methane?

I'm waiting for some one curious enough to take a section of clear vinyl tubing in to the bathroom and verify this for themselves.

Might make for an interesting post if they include the pics.

Will someone please light a match???!

**TomRodgers** · 04-02-2010, 03:47 AM

FINALLY!!!!! I dont know which part of every mentioned method worked....but..

SUNSHINE HAS BRAKES....... at least enuf that when i pull the lever, i cant shove the bike forward....

thats enuf for me to give it a spin a bit later......slow at first to make sure!!!

which brings me to another issue...

Do i lay off work today to ride or go in for double time and a half....hmmmm.

i guess ill go to work to earn overtime to buy more goodies!!!!

Thanks guys.....

Wiring the lever in about 1/4 of the way i left it over night....then bout 20 mins ago..tiny slow pumps......all kinds of "fart bubbles" came out of the spooge hole.....pumped up......bled calipers....and refilled M/C. WHAMMO. solid lever!!!

Thanks bunches amigo's!!!! Maybe this barn find will ride again!!!

GOOD FRIDAY!!!!

**DGXSER** · 04-02-2010, 09:16 AM

Just glad to see another XS11 ready to ride.

Good job Tom!!

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Brake bleeding....AGAIN.....WTF???@)@#*(!

Brake bleeding....AGAIN.....WTF???@)@#*(!

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