Brake lever pulled back to bar after servicing brakes.

[jfheath]

This might seem like an odd problem coming from me. I know my way around the brake system of the ST1300 probably better than many ST1300 owners. Yet this little issue came as a big surprise.

It's been 2 years since I serviced the brakes properly - except for fitting new discs all round last winter, and new pads and a casual flush through, so I thought I'd have a thorough check over. Nothing was wrong, but after 70,000 miles and spring showing no sign of arriving anytime soon.....

So SMC came off, and I separated the caliper from the bracket. I had suspected that the caliper wasn't sliding properly. Popped out the nylon cartridge and checked the tiny compensation port, and ran a 0.012" wire through it - with a bit of effort. Popped out the pistons to check for the state behind. All Ok.
Did the usualy clean of pistons all round - without popping the others out, cleaned and reseated springs, clean slider pins and boots. Cleaned fairly new pads and pad pins.

Then reassembled, new crush washers filled up and throughly bled. My first time without using a vacuum bleeder on this bike, and that all went well.

Everything was rock solid. I was pretty pleased.

Now I don't know what happened after that. I had been putting things back together a bit at a time, popping into the garage whenever I felt like it. So everything was left loose for a couple of days (except the bleed valves and reservoir caps. I know that I lifted the caliper off the front left to double check that I had torqued the banjo bolts. I had. I know that my axle bolt was tight, but I had left the pinch bolts until after I had taken the bike off the ramp.

Both wheels had been out to have new tyres fitted and the fairing was compeltely off.

But two separte occasions the lever pulled straight back to the bar. Once one day - thank goodness the bike was in the garage, but I felt almost as alarmed as if I had been moving. It took two pumps to gte it up to full tightness. Then it did the same two days later.

Both times I can convince myself that it was because I had interfered with the caliper - but I didn't think it was enough to push the pistons in - but I may have done - I wasn't paying attention to that, or I cannot remember exaclty what I did between getting a tight lever and it going soft. Certainly I bled the brake lines without the calipers or pads in place. I use wooden blocks to stop pistons flying across the garage, so the calipers and pads were fitted afterwards, and then pumped up to feel tight.

That was three days ago. Today I took the front calipers off again to check that the spring was positioned properly - I know it can interfere with the movement of the pistons - especially when pads are new. It can drop down below the piston and interfere with the movement. No they were Ok. This time I did move the pistons. So tthey needed pumping out after I had repalced them.

The only thing that I can think of is that the centre piston was never pushed out all of the way - perhaps on the right side - which is subject to the delay valve, and somehow this had affected the alignment of the pads. But I don't think so - the lever was tights and had a really solid feel when squeezed hard.

So I am reasonably happy that I propbably did something to disturb the calipers/pistons on both occasions - without realising. I certainly cannot rule it out. But I wasn't working methodically - sometimes I was takinging a 'shortest job first' approach - so bleeding the rear line came last. But I'm not convinced. I'll find out when I take it out for a test ride.

But can anyone think of anything that I haven't thought of that would cause this behaviour.

 

[Larry Fine]

It sounds like the master cylinder to me. Maybe a speck of schmutz in the bore.

Added: Did you re-check that the MC is still filled?

 

[DannoXYZ]

Yeah, MC isn't sealing.
For whatever reason...

 

[jfheath]

It sounds like the master cylinder to me. Maybe a speck of schmutz in the bore.

Possible, but it never felt as though the lever was struggling to apply the brakes. I left the lever open overnight and this morning it felt just as firm as when I left it.
So I've tied the lever back with a cable tie. If anything is leaking the pressure will find it and there will be room for movement at the lever/cable tie when I get back to it tonight. There is maybe a very tiny bubble in the fluid - I have not bled it again. I'll burb the banjo - although I don't like breaking the seal on those washers. It feels as tight as I like it. Maybe take off the banjo and bleed it with new washers half tightened, burp it and then tighten it up.
Any air in the cylinder behind the primary seal will have escaped through the inlet port. In front of the primary seal, I'd feel it more than that.

It hasn't done the same thing since I stopped disturbing the calipers. There's no evidence of fluid leak around any hose joints.

But I'll certainly investigate those possibilites.

 

[Buckeyechris]

@jfheath

I experienced this same problem after I rebuilt my front calipers. No matter how much I tried to bleed the calipers, the lever was really soft. Here's what Larry had me do:

First, he had me remove the banjo bolt to the front master cylinder (already filled with brake fluid) and asked me to pretend like I was the little Dutch boy by sticking my finger where the bolt had been. Next, he had me gently flick the lever, and tiny bubbles would rise to the top of the reservoir. Then, he had me slowly squeeze the lever, which cause air and fluid to escape past my finger. Before releasing the lever, Larry instructed me to replace the banjo bolt and tighten it finger-tight. He had me squeeze the lever again while slightly loosening the banjo bolt to allow some additional fluid and air to escape. Before releasing the lever this time, Larry instructed me to tighten the banjo bolt. Good and tight is sufficient. In the process of juggling everything, I must have partially released the lever, because there was little resistance when squeezing the lever. Consequently, I had to repeat the process.

For whatever reason, an air bubble likes to form around that banjo fitting. Larry's recommendation solved my problem and allowed me to resume the regular brake bleed sequence.

Chris

 

[newtonhubcap]

Working the a shop environment (Service Manager) we seem to stumble into unforeseen issues on some of the simple lest task such doing brakes and have low brake lever pressure. You can vacuum or pressure bleed ( I prefer pressure when able to) and have no air bubbles but one does. When the occurs we will pull the brake lever into the bar and use a velcro wrap to keep it in that position over night. We will typically see micro bubbles rising into the brake reservoir. Come back in the morning release it - full brake pressure. Hopefully, this will help and resolve your issue.

 

[jfheath]

Thanks for those @Buckeyechris and @newtonhubcap .

The issue is not that the lever is soft. On the contrary, it is nice and firm, and after servicing it feels a fraction firmer than it was before. And it stays like that. I've just been out and burped the banjo union. No air and no change of feel. Still nice and firm.

The issue was that while I was still working on brakes, it went soft - back to the bars soft. A couple of squeezes and it was solid again and then stayed solid. Since it hasn't done it since I the entire brake system and forks were torqued up, I am guessing it was a piston / caliper issue eg moving the pistons.

But I am taking all comments seriously and following them up, because I haven't come across this happening unexpectedly before. So thank you for those. I'll have another bleed this afternoon to see if I can get out any more air.

 

[Mr.E]

Is your brake fluid fresh from a sealed bottle?

I tend to make the mistake of keeping old bottles of brake/clutch fluid and loose track of when they were opened...

 

[Larry Fine]

I tend to make the mistake of keeping old bottles of brake/clutch fluid and loose track of when they were opened...

 

[Tdinova]

Collapsed line?

 

[jfheath]

Is your brake fluid fresh from a sealed bottle?

I tend to make the mistake of keeping old bottles of brake/clutch fluid and loose track of when they were opened...

Yes - sealed cap, adhesive foil sealed. I also keep my opened bottles and date them when they were opened. I use the contents to flush out the old fluid - since the old fluid originally came from the same bottle and is clean an probably only as wet as whats in the lines, I don't mind pumping it all through and sluicing out behind the pistons and exercising the SMC etc. Then flush through and bleed with brand new fluid from a sealed bottle. The remained of that new bottle will be used to flush out the lines the following year.

Ditto !

Collapsed line?

Good thought, the lines are old - 10 years, but the joints and crimps and outer sheaths are still in good condition. I am aware that they need to be replaced and have been looking at what to replace them with, but it's a job for the future, when I have saved up enough pocket money. Maybe this winter. @billo wrote an excellent article about his replacement brake line kit from Hel. I think that I shall follow suit - because it answered all of the questions I had in my mind about those odd joints on the ST1300 system.

Just been and done a bit more bleeding. But that isn't the issue. Nevertheless two very tiny pinprick pubbles emerged and the handlebar feel is now even tighter.

 

[Al st1100]

Sound like bleeding was done properly so just for for giggles make sure both wheels are tight and there is no side play. A little bit can push the pistons in ever so slightly enough to cause that first low pull.

 

[MidLife]

.......I am guessing it was a piston / caliper issue eg moving the pistons.

Then you should see a level drop in the reservoir?

 

[jfheath]

Then you should see a level drop in the reservoir?

I was meaning that perhaps something that I did with the calipers pushed the pistons in, meaning that they would have to be pumped out again the next time I used the lever. The reservoir was closed up att his time - because I had a pretty god tight feel at the lever - but it would have risen back to the line.

 

[jfheath]

Sound like bleeding was done properly so just for for giggles make sure both wheels are tight and there is no side play. A little bit can push the pistons in ever so slightly enough to cause that first low pull.

I am certainly thinking that this may be the cause of the second the event where I got a soft brake lever. But the first ??

Thinks......

The bike was on the ramp. The brakes had been bled and the lever felt solid. So did the pedal. The axle was tightened properly, but the pinch bolts were left loose. I was going to bounce the forks once I had reversed the bike off the ramp. Always an exciting moment. Once down, I went for the brake lever to steady the front wheel in order to get some bounce. (Habit. I shouldn't do that, because it locks the forks in position relative to the wheel. I always do it and I always have to correct myself.) Anyway - the handful of brake resulted in the lever coming straight back to the handlebars.

I know that it doesn't take much to push the pistons far enough to require a considerable pump to make the lever feel tight again. I acquired a warp on my 1100 rear wheel - immediately after having the trye changed. I think they dropped it on the disk..... The warp was negligable, and I couldn't feel it unless the pads were brand new. Otherwise the movement was taken up by the caliper. But until I got a new disk, I'd have to remember to pump up the rear brake before I wanted to use it.

I've just had a thought - triggered by answering that last question. ( I've just finsihed this post and come back to this line. As I type the next bit, I am remembering more and more detail - it just keeps popping back into my head. If you read on, you'll see why.)
.
I wonder if it had something to do with me weighting the pedal overnight. The centre piston would push in the front pads away from the outer pistons. It would also push the caliper back away from the disc - taking the outer pistons with it. I cannot remember my sequence, but I know that I didn't torque the caliper bolts until the bleeding was complete. I was anticipating having to tilt the SMC again - so I wouldn't have tightened the caliper bolts. They would be threaded in but not completely - I never make a bolt look tight if I haven't torqued it.

So worked on the front brakes first. It took much less time than I thought - Fill up each side, get the right sort of feel at the lever, and then bleed each side properly. Rock Solid. The lever felt nice and tight. But the calipers were loose - maybe by 3 threads.

Then do rear brakes. That went smoothly too. I pumped fluid all the way through to the rear outer then the rear centre. The went round the proper sequence. Tilted the SMC, pumped through with the pedal and pumped the SMC a few full length strokes and then the pedal again - put left pads in place. I Pumped up the pistons when I replaced the SMC and left bracket - but again the caliper was not tightened. Got a very good feel on the rear pedal and left it overnight with a massive bench vice tied to the pedal to keep the fluid under pressure.

So having had the front brakes feeling tight, the rear pedal will have pushed the calipers outwards on the loosely fitting mounting bolts, as the piston pushed the pads against the disk surface

Does that make any sense ?

And that would explain why it has never happened before. I'm getting old, and I only work in the garage until I feel I have had enough - then just leave it. Leave it safe - but with notes on the windscreen - eg brakes not secure / front wheel not tight / Rear axle not torqued.
So previously I wouldn't have weighted the brake pedal until the front was all neatly bolted up.

Oh. Goodness. I'd forgotten all about this. I left if for a couple of days !! I'd been crouching down in front of the front wheel. The bike was on the workshop table and there is a short metal plate that sticks up to stop the front wheel from dropping off the front. The ramp was raised about 2 ft. I dropped something - probably the caliper bracket bolt - it rolled under the table. I knelt down to pick it up, and the top of my head went straight into the corner of that plate. Oh deary me - that hurt. It hurt a lot. It wasn't a bang - in my head it sounded more like a crunch. Ice pick.

I thought I'd cracked my skull and left a note for my wife to come and check on me when she got in. A nice neat trangular dent in the top of my head. Surprisingly it didn't bleed much, but I was worried about internal bleeding. Compression doesn't set in as quickly if there's bleeding inside - cos as you get older the brain shrinks, so there's more room for it, therefore less compression of the brain. But I went and sat down with a bandage clamped onto the top of my head and didn't go out again for two days.

Maybe it was worse than I thought - I'd forgotten all about it. It might explain why I am not clear about the exact order of things.

Doh !!

 

[SMSW]

I thought I'd cracked my skull and left a note for my wife to come and check on me when she got in. A nice neat trangular dent in the top of my head. Surprisingly it didn't bleed much, but I was worried about internal bleeding. Compression doesn't set in as quickly if there's bleeding inside - cos as you get older the brain shrinks, so there's more room for it, therefore less compression of the brain. But I went and sat down with a bandage clamped onto the top of my head and didn't go out again for two days.

Maybe it was worse than I thought - I'd forgotten all about it. It might explain why I am not clear about the exact order of things.

Hope you are ok now, John. Those whacks on the head can be really painful. I looked up symptoms of concussions but too many of them sounded like everyday symptoms of ageing so I'll leave that to the docs.

The prunating of the brain (as i call it, as the brain dries out and shrinks w/ age) is the direct cause of the rattling sound we hear...sort of like a loose walnut in its shell. Don't laugh too hard...it might hurt your head.

 

[Al st1100]

The prunating of the brain (as i call it, as the brain dries out and shrinks w/ age) is the direct cause of the rattling sound we hear...sort of like a loose walnut in its shell.

I was wondering what that was, thanks

 

[W0QNX]

I think every time I change the brake pads without bleeding the system this happens to my bike. I thought I read you pressed the pads inwards to remove the wheel leaving air gap between the disc and the pads.

Mine will go clear to the bar after a pad change If I pull it that far. I usually go a half pull in then release and more half pulls until pressure is felt.

If I'm making sense of all your doings I think it will be fine to ride and test.

 

[jfheath]

Thanks for the comments everybody.

In particular @Al st1100 - for the comment about the side play. I suspected that sort of issue but couldn't pin it down to any particular event.
But I went back and considered all of the replies and thought them through again - which helped. And my response to Al - well you saw. The events of the day just started popping back into my head in sequence as I was writing. And I can't believe that I couldn't remember banging my head and satying out of the garage for two days - in case I really messed things up.

Funny how the brain works. Or not. One of my favourite jokes:

My brother's a lot smarter than me. He always seems to know what to do and how to do it. So when I'm struggling, I just think of what my brother would do in the same situation.
And then I do that.

I fancy a walnut now for some reason.

 

[Andrew Shadow]

Then flush through and bleed with brand new fluid from an unsealed bottle.

You must have hit your noggin pretty hard.