went to take the bike in but the shop was booked and i did not feel like waiting around there for 4 hrs.sooooo...
i have an 81.(appears to be correct one master cyl)new lines.rebuilt caliper.rebuilt master cyl.
if my master cyl is not attached/no line etc and i fill up the bowl shouldnt fluid come out the rear of the cyl.?especially if you were to push the cyl in?
how does fluid go from the bowl into front of the cyl(to the left if you look at it on the bike)to be pushed?the hole in mine only allows fluid behind(to the right of the "cup seal" as you look at it/front of bike)---------------i cannot get fluid transfer from the front of cylinder(right) where the inlet hole is to the rear of the cylinder(left...also will be front of seal that pushes fluid)

edit-sounds llike i think i am too good to wait....not true though as i called earlier in the week and thought/assume they would fit me in for a simple bleed job as they told me to come in on sat.-----------also i understand this sounds as confusing as heck but its not i am probably not explaining it clear eneough and i am not sure how too.

 

I can only ask you to check that mastercylinder is correctly assembled.
In right side of bike, brakeline is facing back and rod from pedal is coming from front to back.
Use brake grease ..
From bottom (or left)
First there is that large spring ->
plastic plug ->
rubber seal "cup side" to left or could I say wider edge to left ->
thin washer (brass? non flat) ->
aluminum piston with rubber seal ->
washer ->
c-lock ring.
Then "external" parts, dustcover, rod.

 

1.i didnt use brake grease.-----the rubber cup is not damaged/torn etc. though.
2.there was no thin washer in the kit but it appeared to be made together with the aluminum cyl.
3.there was no washer after the cylinder just the c-clip/lock ring.
i cant see how any of this would change things though.

how exactly does fluid get in front(left) of the rubber cup?
should the hole that allows fluid into the cylinder area be behind(right) of the cup seal or in the front(left)?

 

OK there should be small holes (about 1/8") in end of that aluminium piston.
This can be problem, but not likely... cup seal don't blog inlet port of reservoir.
Fluid is flowing from small hole to reservoir to primary piston. Actually there should be two holes, called the fluid-inlet port and the compensating port, that allow fluid to enter the cylinder. That "cup seal" act as one-way valve keeping fluid volume correct.
When you press the brake pedal, rod pushes fluid from the brake fluid reservoir to flow into a pressure chamber (in that aluminium piston) through a compensating port which results in an increase in the pressure of the entire hydraulic system. This forces fluid through the hydraulic lines. Release of the brake pedal allows the spring within the master cylinder assembly to return that assembly's piston back into position

 

So, what actually happens is.........
There are indeed 2 holes.
a small one that feeds and returns brake fluid to and from the caliper side of the brake "cup", and a larger one that allows fluid to move back and forward between the reservoir and the area between the back of the cup(effectively), and the o-ring that seals the piston from the outside.
When you initially press the brake pedal, there is no pressure build up at all, as the the cup has yet to pass over the small hole, and fluid, at this stage, is merely returned back to the reservoir(which can commonly be seen in the form of a small jet if you have the lid of the master cyl, as the smallness of the feed hole causes some pressure (volume over area), whereas the larger hole tends not to cause such a disturbance, though some turbulence may still be visible).
As the cup passes over the hole, pressure begins to rise in what has now become a closed system between the cup and the brake caliper piston, and accordingly the brake is applied. On modern systems(meaning many many years now, so not really all that modern) a quad type caliper piston seal is commonly used. This is located in a machined recess in the caliper. The recess has a relief(or chamfer) machined into it, so that there can be some deformation of the seal when the piston moves, and that when pressure is released(via the brake pedal being released, the internal spring pushing the cup and m/cyl piston back, the little hole becoming uncovered again, and the fluid being free to equalise in pressure with the atmospheric pressure of the m/cyl reservoir) the seal returns to its quad shape, and draws the caliper piston back with it, thereby preventing the pads from rubbing on the rotor.
As pads wear, the caliper piston makes it way through the quad seal, brake fluid drops in the m/cyl reservoir, and the lid diaphragm flexes to prevent a vacuum from occurring. All self adjusting up to a point.

If you have absolutely nothing connected to the m/cyl, then it will not pressurise, and fluid will not come spurting out when the pedal is depressed. You would have to hold your finger over the end, bleed the m/cyl until you have it pressurised, and then you could get fluid trying to force it's way past your finger. If you take you finger off, the pressure will almost certainly be lost immediately.

Hope the truth helps.

 

yep........i had always thought there were just one hole in a master cyl.there was a clear hole and the other one which i now realize is there appeared to be some sort of cnc machine "grabbing" point.i tried putting a piece of wire from a wire welder through it and couldnt do it.there was just eneough brake fluid there(tiny drop) that it covered the tiny hole.found out later there really is a hole there and used cutting torch tip cleaner and still couldnt clean it.i used basically a tiny thin punch and made thhole bigger.sounds crappy but worked good.i cant feel anything inside--nice and smooth.-------------i should have realized this but i did not.it drove me nuts and threw me for a loop.i often overlook the most simplest things.anyway it is working good.took the bike out for a 350 mile rt today and the rear brakes were nice to have.live and learn.
i wonder how much of a problem this is for others who have a hard time bleeding their brakes.also i noticed after i used the syringe on the brakes i neede to go back and bleed it the normal way...i suppose i was getting air into the caliper when i was trying to tighten while the bleeder was covered with a plastic tube.----that sounds dumb to add but i noticed several people seem to have a hard time after they used the syringe.useing the syringe was much faster and easier for one person but i just needed to do the normal way for the last step to make it perfect.-----might help someone i dunno i hope....this has been a pita but a refresher course i obviously needed.----thanks all.

 

Now listen to me carefully.
The syringe idea is ridiculous.
It pushes all the crap back up into that little hole.
Only people who have no idea as to what they are doing would ever consider using that method.
It is fraught with possible issues.
And it is completely unnecessary.
Just remember also.
That under normal operation, the piston in the m/cyl, only travels part way down the bore.
Then when bleeding, people push it all the way down the bore....... right into all the rubbish that (frequently) lives there.
SHORT STROKES when bleeding. Gotta use your common sense.

 

This method is used as "last" when normal bleeding procedure isn't working.
Usually when bleedeing is needed means that system has been opened and cleaned from "crap"

If there is rubbish in brake system it wouldn't work correctly...changing brake fluid isn't just invention of service people...

 

It's totally ok for you to not know.
But it is not ok at all for you to try and pretend you do.
Brakes are a lot more critical than paint colour or condition.
And it is obvious you know precious little about them.

 

Here are my detailed notes on using a syrunge for brake bleeding. I have been using this technique for a few years as have many others. I have never heard of anyone having a problem with it. It is especially good on the rear brake.

True, if there is grunge in the line then there could be a problem with that grunge getting caught up in the master cylinder. One would have to be aware of this. It does not usually happen.

Brake Fluid Bleeding w/Syringe

You can buy the 60 ml syringe at any drug store, especially one specializing in home medical products. I paid $2.00 for mine a few years ago. Another guy posted about using a syringe from TSC, used for cows or something.

1. discard the needle from the syringe
2. remove lid from master cyl and set it loosely on the master cyl; it must be off of course, but the m cyl must be covered to prevent the fluid from squirting 10' across the shop
3. attach a short clear plastic tube to the end of the syringe; i use tube that is "too small" in diameter - this is important to get a really really really tight seal on the bleeder; i have to force it onto the bleeder with a needle nose pliers
4. use the syringe to empty the m cyl; discard this fluid
5. fill the syringe with new brake fluid
6. let stand for 5 minutes or so for the bubbles to rise out of the syringe/tube
7. attach to bleeder
8. hold it upright and fiddle with the tube until air has risen into syringe
9. loosen the bleeder
10. slowly squeeze the fluid thru
11. do not release pressure on the syringe without tightening the bleeder - some fluid and possibly some air may get drawn back