Article [13] ST1300 - Brake Maintenance - Avoiding the Pitfalls

ATA said:

How critical is it to bleed the PCV?

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If you want crisp, solid braking, follow the bleeding procedure to a Tee. Honda engineering didn’t place that PCV bleed port there because they had extra money, they placed it there for good reason. Get rid of unwanted air bubbles..
The way I envision it, the proportional control valve is at the highest point on the brake tubing, so that’s where the air is going to hang out. If you miss the PCV, you’re gonna have to calculate the tubing from it to the rear bleed nipple, so as the air that was once their at the PCV travels all the way back to that bleeder port and you have to do it quick enough, so the air bubbles don’t migrate back up to the highest point at the PCV.
My recommendation is to use the PCV port in bleeding the system and remove all doubt that the air has been removed from the system.

The problem is that air does not 'flow' like fluid flows. Yes - it goes with the flow, but any bend, any joint, it will hang around and can be difficult to budge. Watch that video of the bubbles in ink coloured water - see the link at the bottom of this. Download the pdf too.

I think that the assumption is that if you don't let air into the system and all you are doing is replacing old fluid with new, then there is no air in there to get rid of ?

But brake fluid is 'hygroscopic' - it absorbs moisture / water. Water gets into the system over time - and braking performance deteriorates as the fluid gets wetter. After 2 years fluid is considered to be too wet to be safe. Water gets into the system past the seals, through microscopic pores in the brake lines, and through joints.

So what has that got to do with air bubbles ? Simple. Water contains dissolved air. Lots of it.

While what you say is largely true - pumping new fluid through to replace old is better than not replacing it at all - you really need to go chasing out every drop of old fluid and air to get the brakes working as they should. Otherwise you are building problems caused by corrosion and 'gunge' build up which are the consequence of not getting rid of all if the old 'wet' fluid and air.

That bleed nipple near to the Proportional Control Valve really helps to get rid of air from a very long circuit, which starts at the rear brake reservoir, goes forward to a high point behind the headlight, thriugh the delay valve, down the front fork legs, through the SMC, back up the fork legs, through the Proportional Control Valve, past the bleed nipple in question, past the battery, and down along the swing arm to the rear caliper outer pistons.

You need to take every opportunity to get rid of old fluid and air that you can.

It is also important to tilt the SMC on the front left caliper bracket for much the same reason.

Take a look at this



It needs to be part of planned maintenance. I always take my fairing off to do mine - not completely necessary, but it becomes part of the winter schedule every year when I do other things too.

ATA said:

How critical is it to bleed the PCV? What if I just Bleed the front/rear calipers? I'll assume there would be some old fluid left in the system. Just asking. Wouldn't it eventually be evacuated if done a couple of times?

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you will have spongy brakes if air is trapped, by bleeding both rear lines you may change the fluid - but will probably need to activate smc multiple times to push fluid through. I think air gets trapped around the pcv as it’s the highpoint of the system, the pcv bleed valve’s a tad lower than it - I had air in mine from SMC replacement so had to do a full bleed - not too bad with a vacuum bleeder.

Great info from some smart ST owners. Thanks for the advice. Looks like I have a right side fairing to remove. Had the brake fluid 'flushed out' last spring in a shop. I doubt they took the fairing off. Not sure if they used a pump either. When you want something done right...do it yourself!

ATA said:

Great info from some smart ST owners. Thanks for the advice. Looks like I have a right side fairing to remove. Had the brake fluid 'flushed out' last spring in a shop. I doubt they took the fairing off. Not sure if they used a pump either. When you want something done right...do it yourself!

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Correct!

There is a way to bleed the PCV valve without taking off the RH fairing. Some on here have done it by lifting the fuel tank and pulling back the right fairing a little. I still choose to remove the right side fairing completely.
Good luck....

Kevcules said:

Correct!

There is a way to bleed the PCV valve without taking off the RH fairing. Some on here have done it by lifting the fuel tank and pulling back the right fairing a little. I still choose to remove the right side fairing completely.
Good luck....

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Anyone use the 'pumps' for brake bleeding? Yea, nay?

In just MY personal opinion, vacuum’s pull fluid through with too much speed and force causing more air, than removing it.
Then you have to clean it, and store it etc.
I’ve had much better luck with a simple check valve like the motion pro hydraulic brake bleeder for about $15 bucks on Amazon .

Igofar said:

In just MY personal opinion, vacuum’s pull fluid through with too much speed and force causing more air, than removing it.
Then you have to clean it, and store it etc.
I’ve had much better luck with a simple check valve like the motion pro hydraulic brake bleeder for about $15 bucks on Amazon .

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Hmm... I've had good success using a Mityvac on several vehicles. Seems to purge/bleed systems well.

ATA said:

Anyone use the 'pumps' for brake bleeding? Yea, nay?

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As @Igofar said, the MotionPro brake bleeder is simpler, less messy, less fiddly, and more than up to the task.
Thought I would try to use my MityVac kit that I've had for years, but Larry talked me out of it. I haven't looked back.
Took me a couple of calls before I realized it's pointless arguing with him, but I did at first, just because I'm stupid stubborn.
In fairness, that was while I was still new around here, and now I know better.
Seriously -- just do as he says; he's the real deal. No point in reinventing the wheel.
MityVac works in many applications, but with this bike there are so many bleed points, and there is a specific sequence. This is not the same as any average brake bleeding task. Yes you "can" use another method, but... see above.

Igofar said:

In just MY personal opinion, vacuum’s pull fluid through with too much speed and force causing more air, than removing it.

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That will happen if the reservoir is allowed to run empty, not because a vacuum pump is being used. Allowing the reservoir to run empty will have the same effect no matter what method of bleeding is being employed.

I can see both points, but wouldn't there be an increased chance of introducing air, if for no other reason than the turbulence created by using more force than necessary?
Really not trying to start an argument... just thinking / typing out loud...

If the reservoir never runs dry, air is not introduced in to the system no matter how quickly the fluid flows. To make it manageable, vacuum pumps have adjustable throttles on them to control the vacuum so the system can be bled as slowly or quickly as one can manage the fluid flow.

If air is drawn in to the system, it is not the tools fault regardless of which tool is being used.

Andrew Shadow said:

If air is drawn in to the system, it is not the tools fault regardless of which tool is being used.

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No argument there; even *I* can understand this much.

Not trying to impose my will, but I’ve had several seasoned master mechanics demonstrate how well their vacuum systems worked, only to remove a lot of air out of the systems after they were finished by using the check valve method instead.

I’ve been wrenching for 47 years and never had the desire to buy a vacuum bleeder, wife and I have been a tag team for bleeding until Igofar gave me the idea of the motion pro one way check valve bleeder.
One person job now, but the wife always hints that she can stomp on the brake pedal if needed, she knows the drill after 40 years.

I don't dispute that at all Larry, it actually doesn't surprise me. In my experience most shops do not do that good of a job bleeding brake systems because they don't take the time to run enough fluid through the system to make sure that they have chased all of the air out. I would hope that you would agree that if there is air remaining in the system after it was bled with a vacuum bleeder, it is because it was not properly bled, not because a vacuum bleeder was used.

As a footnote:
The best flushing and bleeding of a brake system that I have ever been able to accomplish is when I had access to a pressure bleeder. It is quite striking to see how much more contaminant a pressure bleeder forces out of a brake system in addition to even more air that hides in the far away recesses. I have never experienced such rock hard and responsive brakes as when I have used a pressure bleeder.

I’ve used pressure bleeders, reverse bleeders, trigger oil cans used to reverse bleed, gravity, vacuums, etc.
Like you said, the correct methods and techniques are the key, and knowing where air hides etc.
If you know theses tricks, you can get just as firm of a lever with a $15 dollar check valve, and not having to clean it afterwards.
Pushing fluid is always better than sucking or pulling fluid.

Andrew Shadow said:

As a footnote:
The best flushing and bleeding of a brake system that I have ever been able to accomplish is when I had access to a pressure bleeder. It is quite striking to see how much more contaminant a pressure bleeder forces out of a brake system in addition to even more air that hides in the far away recesses. I have never experienced such rock hard and responsive brakes as when I have used a pressure bleeder.

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I agree !!

I built my own pressure bleeder using a one gallon lawn and garden sprayer. Took me maybe two hours at the most to modify it ... and saved a boatload of $$$ over a dedicated unit.

I use it on the two MBs and Jeep, and have used it on the ST ... it's quick, easy, and just one person required.

Here's a great video how to build one

Sadlsor said:

As @Igofar said, the MotionPro brake bleeder is simpler, less messy, less fiddly, and more than up to the task.
Thought I would try to use my MityVac kit that I've had for years, but Larry talked me out of it. I haven't looked back.
Took me a couple of calls before I realized it's pointless arguing with him, but I did at first, just because I'm stupid stubborn.
In fairness, that was while I was still new around here, and now I know better.
Seriously -- just do as he says; he's the real deal. No point in reinventing the wheel.
MityVac works in many applications, but with this bike there are so many bleed points, and there is a specific sequence. This is not the same as any average brake bleeding task. Yes you "can" use another method, but... see above.

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I know; I have done it twice using a Mityvac. Only thing I found to watch for is making certain you keep the reservoir from emptying.

core-aggie said:

I agree !!

I built my own pressure bleeder using a one gallon lawn and garden sprayer. Took me maybe two hours at the most to modify it ... and saved a boatload of $$$ over a dedicated unit.

I use it on the two MBs and Jeep, and have used it on the ST ... it's quick, easy, and just one person required.

Here's a great video how to build one

Click to expand...

That's pretty slick. Here's a video of him using the bleeder he made.