What is wrong with my brakes??

[JimmyR]

As some of you may know, I'm restoring/rebuilding an '82 GS1100G. As part of this I have rebuilt the brakes and am trying to bleed the front brakes. I have a brand new Suzuki master cylinder, new Goodridge stainless braided lines and bolts and have blasted and powdercoated the calipers in black. I have cleaned everything scrupulously and have new pads in place. I replaced all the seals and boots. In fact the seals were installed by a Suzuki tech who just happens to be a brake expert, having worked in a brake shop for years! I was having trouble with them...

So I'm bleeding the brakes as I have done in the past, but I have never bled a system with two calipers off the same cylinder, if that makes any difference. I have bled both calipers until no air bubbles are visible and locked off the bleed nipples. Even though there is just enough pressure to light up the new hydraulic brake light there seems to be very little pressure on the lever. I seriously doubt it would be safe to ride. It is easy to pull the lever to the grip.

I have inspected all over. All the banjo bolts are tight and all have the crush washers each side. I can't find any leaking fluid anywhere. Why don't I have any pressure on the lever? To bleed I squeeze the lever, hold it while I release the bleed screw a little, some fluid comes out and down my clear line and I tighten the screw again before releasing the lever. I can't see any bubbles in the fluid.

Thanks guys!

[tkent02]

There are a few tricks... Here's one. Try tying the lever back as tight as it will go for a few hours, or overnight. Then tap the hoses here and there, the idea is to get all of the bubbles to float up to the top of the lines. Then later with the lever still tied back, release the banjo bolt from the master cylinder, you will hear a PHFFFT as the pressure escapes, that sound is air coming out. You will want to wrap a rag around it before you release the bolt, as brake fluid will spray onto everything otherwise. Each time you do this, the lever will get firmer.

[koolaid_kid]

Can you pump them up with multiple squeezing of the lever?
Are the seals you speak of the ones in each caliper?
Sounds like you still have air in the lines or the M/C.
Did you go back to the stock configuration of 1 line going to the T, then 1 line going to each caliper?
Did you bleed the M/C first? I have read of instances where there is a small bubble trapped in the M/C itself.
When I used that method I got the best results by putting a loop in the clear line to make sure no bubbles found their way back into the calipers. The bubbles would float to the top of the loop instead of going back into the caliper.
I use a MityVac now and it is much easier.

[chuck hahn]

Can also go to Oreillys or Auto Zone and get a mighty vac from their tool loaner program. That baby will suck a good amount, if not every micro speck, of residual air out. Then as Tom said..pump the lever up as hard as you can and tie it back over night. next morning youll notice a very hard lever. Ive never had to loosen any banjo bolts to purge air when i use my mighty vac. Not saying his suggestion isnt valid and useful but the mighty vac almost always gets all the air out. Dont be afraid to run a few resivoirs worth of luid thru to be sure.

[JimmyR]

I have used the original splitter which bolts under the lower triple tree, so routing is the same as stock. Pumping does nothing to increase pressure. I did in fact use a Mityvac hand pump to bring the fluid down the lines! What surprises me is that I have done everything I would do on my other bike (except it only has a single caliper on the front) but I don't have any pressure. Well, I have some but not much.

I also rang my local Suzuki dealer who knows about brakes and he suggested the tie the lever to the grip thing too. He aslo suggested that I take the calipers off the wheels, add some filler between the pads (I have used folded up cardboard) so that the pistons don't pop out and suspend them higher than the master cylinder. So right now I have my bike in the garage with the calipers hanging just a bit higher than the grips and have the lever pulled against the grip with a zip tie.

And yes - I've pumped quite a bit of fluid through now! I'll see how it is tomorrow morning. Thanks heaps for the suggestions guys. This site is such an incredible resource - you guys are great.

[Colin Green]

Does your new MC have the right diameter piston (16mm rather than 14mm)?

Pop the MC cover off and look for the little hole in the bottom of the MC (back pressure relief overflow) and check how much lever travel occurs before the fluid stops squirting up out of the hole. If the piston seal is set too far back from the little hole, a fair amount of lever travel is wasted as it escapes through this hole before any pressure is built up in the MC.

You do need a bit of travel before the hole is sealed or the brakes could lock up due to heat induced fluid expansion. 1mm should be heaps.

I had a 3mm+ gap which translated to about 33% of lever travel being wasted and if squeezed hard enough the lever would come all the way back to the grip. A 3mm ali spacer between the piston head and seal fixed it good.

Oh yeah! another thing. I found that drumming/pulsing the lever by tapping it hard and fast enough to sort of pulse the fluid without any real pressure, would clear the end of the MC of trapped air (a couple or three short streams of iddy biddy bubbles).

Another trick is to remove the lower caliper bolt and pivot the calipers up so the corner of the pad is only just laping the disc. Squeeze the lever hard to close the gap between the pads (pushing the caliper pistons outward over the seals) then gently but firmly force the calipers back into position. The seals seem to rotate a little before the piston slides past them and this can result in a gap between the pads and discs when the seal rotates back as the pressure comes off the pistons. That little gap soaks up another 5 or 10% of the lever travel and I find I have to do this a few times as the pads wear down in order to maintain a good feel at the lever.

[JimmyR]

Well the MC is brand new so I would imagine it has the right size piston. I would hope it does! I did notice that whenever I squeeze the lever quite a fountain of fluid comes up from the reservoir. In fact when bleeding the brakes I have to squeeze quite slowly or else I squirt brake fluid everywhere. When I bleed the brakes on my Harley it doesn't do that. I see a bit of bubbling or something but no big fountain.

[JimmyR]

So I left the brakes all last night with the lever held back by a zip tie. I put the calipers back onto the wheels last night. So this morning there was no change - still very weak pressure. Bled the brakes both sides some more - still all clear and no bubbles. So now I am leaving it overnight with the lever held back again but with both calipers suspended above the bars. Wish me luck!

[chuck hahn]

You cant leave the lever back with the calipers off unless you put something in between the pads so you can build up the pressure. Pumping them up without a spacer, you may pump them too far and push the pistons out of the calipers...dont want that to happen. If you rebled them and its crystal clear fluid and no buibbles, then by your description of symptoms..I am going to point at the master cyclinder needing a rebuild or a bigger master all together.

[850GT_Rider]

Also make sure:

• The brake line goes DOWN as it leaves the master cylinder. If it goes up at all, you can trap air in the 'hump'. (Do NOT ask me how I know this )
• Same for the "T". Overall path for the brake lines from the master cylinder, to the T, to the calipers has to be downhill all the way.
• You do have the calipers on the correct sides, so the brake lines enter the bottom and the bleeder screws are on top?

As to hanging the calipers - isn't the purpose of squeezing and tying back the brake lever intended to allow any air to migrate up to the master cylinder? If the calipers are elevated AND the lever is tied back, doesn't that defeat the purpose?

[JimmyR]

Yeah that's why I put the calipers back on the bike yesterday! But I am willing to try anything now as I seem to be getting nowhere. I think the idea was to bleed the MC.

And yes I put some folded up cardboard between the pads when I took them off before squeezing the lever. :-) As the lines are arranged when the calipers are on the bike all lines do point down. The line is flattish as it comes out of the MC but still definitely downhill. I guess it could be that the splitter is holding some air - how to clear it I don't really know. I have tried tapping various bits...

The master cylinder I have is a brand new Suzuki replacement for this bike. My stock lever fits it perfectly, it is identical to the stock part except that it doesn't look like crap! I definitely have the calipers on the correct sides as I read someone else's post where they had them on the wrong sides! So yes, the bleeder is at the top of the calipers.

My plan for now is to see how it is tomorrow morning. If it is not right tomorrow morning I am going to pull the calipers off and apart again and recheck that everything is good, even though I can find no leaks anywhere. The only other thing I can think might be an issue is that I cleaned out some of the thread of the bleeder and banjo bolts after I put the seals in, so maybe some crap fell down into the piston chamber when I did that. I doubt that it would result in this situation but if there is something in there It can't hurt to get it out. I don't even know if anything DID fall in there, but am getting desperate enough to check!

Koolaid Kid - how do you bleed the MC first?

[Steve]

But I am willing to try anything now as I seem to be getting nowhere. I think the idea was to bleed the MC.
... Koolaid Kid - how do you bleed the MC first?

OK, I'm not the Kid, but I'll give it a shot.

- Get some help, this takes more than two hands.
- Remove the brake lever.
- Loosen the banjo bolt at the master cylinder.
- Use a Phillips screwdriver or a wooden dowel to push the piston as far as - it will go. This might be farther than the lever will push it.
- While still holding the piston in, tighten the banjo bolt.
- Release the piston.
- Continue bleeding the brakes as normal.

Since the outlet is smaller than the cylinder bore, there is a chance that an air bubble has gotten trapped it that area abouve the outlet. Pushing the piston all the way in will force it through the outlet.

.

[koolaid_kid]

Thanks Steve. I am kinda busy this afternoon performing a cardinal motorcycle sin: Putting a new chain on used sprockets. Don't tell anyone though.

[1_v8_merc]

make sure the MC is holding pressure too.
(just to verify)
Just plug your thumb over the hole(where banjo connects)
And start pumping the lever a bunch, until the pressure pushes hard on your finger, keep the Lever Squeezed In a little bit, and barely let your thumb off, a tiny bit. As the fluid/air shoots out, plug it back up and repeat the process a few times.
Once you start getting Straight Fluid coming out, you're good.

I use this process and immediately hook up the Banjo, and usually have good luck and very little air in the system. I would still use a mighty-vac though, it speeds up the whole process.

[Colin Green]

You have lots of good advice here, but I will say it one more time.

If you are seeing a big long lasting jet of fluid squirting up out of the MC when you squeeze the lever (which you indicated to be the case) you are probably loosing a big chunk of your lever travel before any fluid pressure is applied to the calipers. Manufacturing variations may result in the overflow hole being too far away from the piston seal. Can't hurt to check it out.

I know its a new MC and it's supposed to be for your bike, but that doesn't mean that it is the correct size (people make mistakes all the time). If you are checking everything out anyway, you may as well check the piston diameter and be sure. If it is too small the amount of lever travel required to move the required volume of fluid will be greater.


The smaller hole on the right of the picture is the little pressure relief hole.

As can be seen in the picture, a spacer between the end of this aftermarket piston and seal was required to reduce the amount of lever travel required before the calipers would bite the discs. I ended up with about .5 of a mm of piston travel left before the hole was blocked by the seal.