Hi again,  I have posted questions about this before and got some very good suggestions.  However still no luck, so I decided to ask one more time, this time detailing what I am doing step by step.  Hopefully someone sees something.

I had to rebuild the front brake caliper, and I also cleaned the master cyclinder, so the brake system is full of air at both ends.  After I assembled everything together I tried to bleed it as follows:

1. Pour brake fluid into the master cylinder
2. squeeze the brakes a few times to get the fluid going down to the caliper
3. start bleeding by
   a. attaching a 1/4" clear tubing to the bleeder valve (width is such that it barely fits if lubricated with clean brake fluid).
   b. putting the other end into a plastic bottle partially filled with fluid.  Set the lever to #1 on the dial.
   c. opening the valve a little.  Squeezing the lever.  Closing the valve.  Releasing the lever.  Repeating.
   d. As needed I added fluid to the reservoir never letting it drop below the line
   

Problem is that doing all that never seemed to bring the resistance of the lever to higher than whatever the spring of the piston in the master cylinder offers.  As I squeeze, I can see the caliper's pistons come out, especially towards the very end of the lever travel, and as I release they retract right back up.

Someone mentioned the possibility of an air bubble forming inside the master cylinder where the hose joins it, which wouldn't normally get blead.  The method for getting rid of it was to squeeze the lever, crack open the connection a little bit, and retighten.  I did it that (squeezed lever, opened with a spanner until fluid started coming out, and retightened).  No go

I have a feeling that somehow I am letting the air back in during this bleeding process, but not sure.  From what you could see, is there anything I am missing or should watch out for?  The fluid I am using is this:

http://www.cbxmanmotorcycles.com/Castrol-Motorcycle-Brake-Fluid.aspx

Castrol GTLMA.  It doesn't say DOT 4, but it says in small letters that it exceeds dot3 and dot4 specs.  Also it doesn't say anywhere that it's synthetic and judging by the price it's very unlikley that it is.  Is the fluid right?  Seems to work in my rear brake ok, but front brake.... errrrgghhh!!! just can't bleed it.  Any ideas?

Thanks

The fluid you're using should be fine.  Just don't use DOT 5 silicone fluid.  It compresses more than conventional fluid and give a squishy feel.  As for the bleeding process how fast are you pumping the lever?  Do it slowly.  If there is air in the system slow pumps keep the airbubles from breaking up into several small ones.  Is there anything in the caliper to calmp to?   Sometimes if I'm having trouble I'll place a wood block in the caliper.   

X-ray could you please elaborate on what you mean by if there is anything to clamp to and what you do with the wooden stick?

I guess I'm asking if the caliper is on the bike.  I do mine off with a block of wood in the caliper to prevent the pistons coming out.  I just dont like accidently getting brake fluid all over everything. 
I bleed the system 'till the pistons clamp down on hte wood and then reinstall.  I hand spin the front wheel and continue to bleed from there. 

How long have you let the bike sit between bleeding attempts?  Sometimes letting the air collect into one big bubble helps.

If worse comes to worse you can purchase a hand bleeder, "mighty vac" is a brand I think but there are many generics out there fairly cheap.

Oh i see, no I did put it back on the wheel.  And it did seat for a week between attempts as i can only do anything on weekends.   

I had this exact issue a couple of weeks ago and it took forever to resolve.

Two suggestions:

1) Bleed the master cylinder by disconnecting the line at the MC.  Cover the gas tank and everything else in range (especially the dash).  Hold a finger tightly over the MC outlet and slowly pump the MC a few times.  Hold your finger tight so as not to let air back in the MC in between pumps (an assistant might be handy).  The fluid will pump out around your finger in a crude spray (hence the massive covering!).  Reconnect the line.

2) Buy a Mity-Vac.  Mine was $36.99 at a local chain auto parts store.  I never got the air out with conventional bleeding (and I have bled brakes and clutches in cars for 30 years).  I recycled the fluid (I had all new, clean fluid) as I pulled it out with the Mity-Vac and put it back in the MC (make sure it has a little time to rest so the bubbles settle up and out of the fluid before you pour it back).

Be patient -- mine took way too long.   I thought something was very wrong.  It wasn't.  It is just very inefficient trying to bleed a system with the bleed screw two feet lower than the MC.

This is all I can offer.Mighty-Vacs are great.
If you can find some thing to hold the pistons into the caliper,while bleeding,would help.
Go very,very slooooow.
Keep the bleed screw pointing as close to srteight up as possible.Air rises.

Here is something that works for me.

Fill master cylinder.Slowly pull the lever while looking in the resivior.WEAR GOGGLES!
Fill as nessasary.When you can pull the lever and the fluid level doesn't drop.You're ready
for my little tricks.Simutaniously,pull the lever in while opening the bolt holding the line to the
caliper.Tighten bolt before the lever is all the way in.Check fluid level.I do this twice.Next,I use
the handle of a screw driver and lightly tap the caliper.Tap once count to 3,and repeat a few times.
Let it set for about 10 minutes,while I clean up my hands,tools and bike.Then I bleed as normal using the
bottle and tubing method.

Hope this helps.

Sorry for the second post.My bleed screws are rusty and need to be replaced.
Does any one use speed bleeders or some other bleed valve that doesn't rust?
If so,can you post part numbers and a supplier?

Thanks for the pointers all!  Damn I wish I could try it tomorrow but due to work / schedule will only get to it next weekend.  Hopefully I'll find mighty-vac at a nearby pep-boys in the mean time.  It's a torture living through this kind of weawther without functional brakes 

Quote from: GSinUS on May 28, 2007, 11:09:11 AM
1. Pour brake fluid into the master cylinder
2. squeeze the brakes a few times to get the fluid going down to the caliper
3. start bleeding by
   a. attaching a 1/4" clear tubing to the bleeder valve (width is such that it barely fits if lubricated with clean brake fluid).
   b. putting the other end into a plastic bottle partially filled with fluid.  Set the lever to #1 on the dial.
   c. opening the valve a little.  Squeezing the lever.  Closing the valve.  Releasing the lever.  Repeating.
   d. As needed I added fluid to the reservoir never letting it drop below the line

Make sure that the plastic "receiving" bottle is higher than the brake caliper itself--it's a rarely mentioned detailed for some reason and a critical one, too. Air bubbles prefer to rise and will easily resist the meager pressure of the master cylinder if you try to pump them down. Try opening the bleeder valve a bit more in Step C. Perhaps you're not be opening it far enough? When I rebuilt and refilled both brake systems this winter, it was quite surprising to discover just how long it took to fill the lines and piston chambers. The day after the bike was up an running, I stumbled over a Mity-Vac clone on sale for $20.   

Wow indeed my "receiving" bottle was on the ground!  Could this be it?  At this point i'll cling to any clue offering hope.  Is everyone bleeding their brakes with the bottle raised above the caliper?

Quote from: ben2go on May 28, 2007, 06:22:21 PM
Sorry for the second post.My bleed screws are rusty and need to be replaced.
Does any one use speed bleeders or some other bleed valve that doesn't rust?
If so,can you post part numbers and a supplier?

I don't think I've ever seen a non-rusty bleed screw!  I did put teflon tape around mine (as per the Mity-Vac instructions) so that air couldn't enter around the threads while the valve was open during the suction-bleeding process.

Quote from: GSinUS on May 28, 2007, 08:06:14 PM
Wow indeed my "receiving" bottle was on the ground!  Could this be it?  At this point i'll cling to any clue offering hope.  Is everyone bleeding their brakes with the bottle raised above the caliper?

You know,I never thought to mention that.I always had the bottom of the bottle
(or catch can on mighty-vac)level with the top of the caliper.I usually fill the container
I'm using about an inch deep with fresh fluid.

HERE IS AN IMPORTANT SAFETY TIP:ALWAYS USE NEW SEALED BRAKE FLUID.
WHEN BRAKE FLUID SITS,WITHOUT THE SEAL,CONDENSATION COLLECTS INSIDE
THE BOTTLE AND BECOMES SUSPENDED.THIS CAUSES SEALS TO FAIL,PARTS TO
CORRODE AND SEIZE UP.NOT TO MENTION,RUBBER HOSES WILL SWELL SHUT.

PLEASE,BE SAFE,AND TAKE A CHECK RIDE IN AN AREA WHERE THERE ARE NO VEHICLES.

After that,ride fast,take chances. Just kidding. Ride safe.

I5

Quote from: Wrecent_Wryder on May 29, 2007, 06:03:58 AM
I'm going to be facing this soon- I have new pads, brake lines, fluid, rear shock, front springs and fork brace and fork oil on the shelf waiting. Starting to get a little concerned, wondering how long I might be stuck without the bike if it doesn't go well...

If you're careful and don't break any thing,a weekend.If things go horribly wrong,maybe a couple weeks.Buy a work shop manual.Use the link on GSTwin home page,it helps support this site.Also,you will need a special tool to completely disassemble the fork.If you're just replacing the springs,there's no need for the tool.Hope this helps.

I was told years ago by an old hand to bleed brakes with the engine ticking over. The vibration agitates the fluid in the line and helps to prevent bubbles of air from becoming lodged. I thought it was BS..........until I tried it myself!!!

how offten should one do this