Bleeding front brakes question from a noob

[BigV]

Hi all

Going to be changing my front pads on my K7 SV650S, and will need to replace the brake fluid after new pads are fitted...colour of the fluid in the reservoir indicates it needs a change. Have searched a bit but cant find the answers to my questions.

I checked the manual and it shows how to replace the fluid...but some questions, as I have not done this before:


It says keep the bike level...huh? With the std kickstand it comes with...now how must I do that - balance the bike and change the fluid at the same time? WTF?
It states to suck out the old liquid from the reservoir, and then bleed the brakes while topping up the reservoir. Wont the old and new brake fluid mix then?
I see both 2 front brake calipers have bleed nipples, does this mean I have to bleed the right caliper and then the left caliper after? So I have to bleed the brakes twice essentially?
The tutorials I have seen on YouTube, most guys use the tube and bottle trick...is it good enough or should I save the hassle and buy a bleeding vacuum kit?


Cheers ;)

[NTECUK]

Paddock stand. They are so handy.
Keeping the bike upright and level
Less likely to suck air in the system.

Also look up reverse bleeding with a syring.

Vac bleeder you can DIY one from a vacuum cleaner .
Have a Google

[johnnyrod]

You can do it on the sidestand, and if it's just a flush out then it's quick and easy. Yes the fluid mixes a bit but don't worry. Turn the bars left, the right caliper nipple should be at the high point, attach your tubing and make sure the nipple actually turns (maybe use a socket first to crack it). top off reservoir, open the nipple a little, and pump the brake lever. If you open it too far it'll tend to suck back. When the level drops near the outlet of the reservoir, top it up and keep going until the good stuff comes out the bottom. When it is clean, do the thing of slowly squeezing the lever while closing off the nipple, so fluid is coming out slowly while you close it i.e. no air is sucking back. Next put bars to full right lock (cap the reservoir for this if you want) and repeat on the left side. Once you're done put a bit of fluid in the top so it's mostly full. As long as it doesn't run dry while you're flushing, you'll be fine. I've never used a vacuum bleeder in 25 years, they're really only useful if the master cylinder is totally dry, but you can work without one then anyway.

[Blapper]

+1 for reverse filling. Cheapest and easiest and foolproof providing you can get a LARGE enough syringe.

[Blueperson]

Once you've finished cable-tie the brake lever to the bars (ie. brake on full) and leave it overnight to remove any stray bubbles of air

[johnnyrod]

Can do - leave it on full left lock i.e. the master cylinder banjo bolt is pointing bolt-head down, so the bubbles collect at the m/cyl end. When you release the cable tie they'll suck into the reservoir. It also pushes the brake pistons out for a long time, so if they have been sitting back a bit in the calipers (which causes excess travel) then they'll get used to being in the right place.

[R1ffR4ff]

1:If you don't have a paddock stand you can get the bike up closer to vertical by putting a piece of thick wood under the side-stand but do this only of firm level ground(Concrete/Tarmac drive etc).Don't make it too thick for obvious reasons as you don't want the bike to go over.

If you have a garage you can use a ratchet lock strap to secure the bike to something.

I use,"Old School" methods for bleeding my brakes once I have pumped all the old fluid out.

A piece of 6mm internal diameter tubing into a jar on the floor and the other end on the bleed nipple.
I quarter fill the jar with new or old brake fluid and make sure the pipe is the right length to go under the top of the fluid by cutting it to the length required.This acts as a one-way valve disallowing air to get back into the system whilst bleeding.




Open right hand bleed nipple.Top up the M/C(Master Cylinder)with new fluid.Watch the level whilst pumping the lever and when it drops about half way top-up the M/C and repeat until you see the fluid and air bubbles go into the jar.

If for some reason you cannot pump the fluid through it just means the MC needs priming.Easy trick to this.Spit on your hand and spread it around and place it on top of the MC and press hard to form a seal and pump the lever again.You should get fluid though.

When you are happy with no or few bubbles coming through into the fluid tighten the bleed nipple but just firmly,do not over-tighten.

Repeat bleed for left hand side.
Come back and do right and side
and then do the left again.

Doesn't take long when you get the hang of it and you don't have to change the fluid that often compared with other maintenance jobs.

Might Vacs are good but expensive and I've never needed one.A syringe and back filling is a good way to go if as above you can find the right one.

HTH :)

Tip:
You can use old supermarket plastic carrier bags to cover the paintwork and parts of the bike that might get fluid on them.This is worth doing as brake fluid is very corrosive.I keep my old brake fluid as a rust and paint remover for small parts.Just let the bits sit in them for a few days.

Also a 50/50 mix of Brake fluid and Acetone makes a great rust release fluid.Way better than WD40 or similar.

[NTECUK]

http://s289.photobucket.com/user/decosse01/media/Misc/normal_speed_bleed.jpg.htmlAmazon etc sell syringes.
The fact your doing it one off your ok with a normal one .
Sealy do one that is ok with the brake fluid on the seals
Sealey VS404 Oil & Brake Fluid Inspection Syringe 200ml

The old cylinder vac and two strok

e oil container vac bleeder
http://oi289.photobucket.com/albums/ll224/decosse01/Misc/normal_speed_bleed.jpg

[shiftin_gear98]

Pretty sure this is the one I use.
http://www.ebay.co.uk/itm/Brake-Bleeding-Large-Syringe-Tube-Also-Gearbox-Motorcycle-Fork-Oil-Filling-/161657955017?hash=item25a390a2c9:m:m9CaC5HJIf0HOyG JM_BB-0w

[SV650rules]

This company sells a non-return valve, wonder what their returns policy has to say about non-return stuff LOL - Also I often wonder if you should ever buy a battery that is shipped free of charge.

http://www.ebay.co.uk/itm/New-Motorcycle-Car-Brake-Bleeder-Clutch-Bleed-Bleeding-Tool-Kit-Little-Bleeder/401280374934?_trksid=p2047675.c100623.m-1&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%2 6asc%3D44293%26meid%3D522637ff8a92482eb555a8bad1ac 1d13%26pid%3D100623%26rk%3D4%26rkt%3D6%26mehot%3Da g%26sd%3D161657955017

https://www.youtube.com/watch?v=1iSN2vc5-b0


The problem I see with reverse bleeding, especially on ABS systems is that dirty fluid from slave cylinders and lines is being forced back into the system not sucked out, there should be filters in ABS system and these could get blocked by crud, which in any case may be pushed back into system once brakes are used again. The dirtiest most contaminated fluid is likely to be in lower parts of system.

IMHO maybe a combination is best, get clean fluid into system by sucking from the bleed nipples on calipers (or squeezing brake lever / undo nipple etc, or with non-return valve as in link above) and then use reverse bleeding as a more effective way of getting any remaining air bubbles out.

Getting air into an ABS system actuator is not normally good news as it can be devilish hard to get it out again.

[BigV]

Wow, thanks for all the replies and the long detailed ones, really appreciate it. Pretty much have my questions answered, and some great tips I will use! Thanks again guys!!! :D

[NTECUK]

I've got into the habit of get as much of the old fluid out of the Master.
Suck it through with the vac bleeder.
If it's not as good as it should be ( my old zx6 is bad for this) then back bleed it.
But there's More chances of fluid spill if you get carried away.

[Bibio]

Once you've finished cable-tie the brake lever to the bars (ie. brake on full) and leave it overnight to remove any stray bubbles of air

this does nothing apart from turn the big bubbles into little bubbles. there is nowhere for the air bubbles to go as the system is in 'compression' e.g. closed. the only way to get rid of air in a braking system is to bleed it out.

there are other reasons why this works but it has nothing to do with getting rid of air bubbles.

[aesmith]

I don't see the point in reverse bleeding if you're changing the fluid rather than filling after it's been drained out. Just pump through the system normally, and take care topping up the reservoir as the fluid can trap bubbles if you pour it in too fast.

[SV650rules]

Highest part of master cylinder (which is highest part of system) is open to reservoir when piston is in its normal position (as soon as piston moves forward the equalisation port is closed off), that is to allow fluid in and air out. Decent hydraulic systems are designed to be self-bleeding.

[Blapper]

This company sells a non-return valve, wonder what their returns policy has to say about non-return stuff LOL - Also I often wonder if you should ever buy a battery that is shipped free of charge.

http://www.ebay.co.uk/itm/New-Motorcycle-Car-Brake-Bleeder-Clutch-Bleed-Bleeding-Tool-Kit-Little-Bleeder/401280374934?_trksid=p2047675.c100623.m-1&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%2 6asc%3D44293%26meid%3D522637ff8a92482eb555a8bad1ac 1d13%26pid%3D100623%26rk%3D4%26rkt%3D6%26mehot%3Da g%26sd%3D161657955017

https://www.youtube.com/watch?v=1iSN2vc5-b0


The problem I see with reverse bleeding, especially on ABS systems is that dirty fluid from slave cylinders and lines is being forced back into the system not sucked out, there should be filters in ABS system and these could get blocked by crud, which in any case may be pushed back into system once brakes are used again. The dirtiest most contaminated fluid is likely to be in lower parts of system.

IMHO maybe a combination is best, get clean fluid into system by sucking from the bleed nipples on calipers (or squeezing brake lever / undo nipple etc, or with non-return valve as in link above) and then use reverse bleeding as a more effective way of getting any remaining air bubbles out.

Getting air into an ABS system actuator is not normally good news as it can be devilish hard to get it out again.Good point. My ol' curvy don't have that new-fangled ABS stuff...

I don't see the point in reverse bleeding if you're changing the fluid rather than filling after it's been drained out. Just pump through the system normally, and take care topping up the reservoir as the fluid can trap bubbles if you pour it in too fast.

It's all about preventing air getting past the thread of the bleed nipple.

this does nothing apart from turn the big bubbles into little bubbles. there is nowhere for the air bubbles to go as the system is in 'compression' e.g. closed. the only way to get rid of air in a braking system is to bleed it out.

there are other reasons why this works but it has nothing to do with getting rid of air bubbles.

Yeah, weirdest thing. You would think that the air bubbles would be better off rising naturally up through the tiny hole that allows fluid to make up for pad wear etc. (which can only happen when the lever is out) and I don't understand how loads of small bubbles gives a less spongy lever than one big one, but it does work. I was sure it was BS until I tried it!

[Bibio]

I don't understand how loads of small bubbles gives a less spongy lever than one big one,

simple. with a large bubble you have fluid either side of the bubble (large bubble makes up a chamber) and when you pull the brake lever the fluid above gets compressed then compresses the bubble which gives less compression of the fluid below. with lots of tiny bubbles you have fluid surrounding the bubbles (no chamber) so gives a direct path for the fluid to compress. the tiny bubbles still compress so gives less performance than no bubbles.

another thing (especially so with curvy rear brakes) is to crack the banjo bolt at the MC on the pull then close just like bleeding at a nipple. its know for air to get trapped at banjo bolt unions more so than in the lines.

best thing to do is let the braking system settle in then do a second bleed.

if you dont have a proper bleeding kit and just using a tube and jar you must make sure that the tube at the jar is submersed in fluid or you will draw air unless you do the 'pull,open,close' method on the lever/nipple.

always have a bucket of water and a wet rag handy when bleeding brakes, brake fluid is hygroscopic and water neutralises/dilutes it enough not to cause damage to paint if you have a spill.

[Bibio]

if your changing the pads on your bike then bets are that the callipers are needing serviced as well. no amount of new pads or fluid change will improve braking performance if you have sticking callipers.

[SV650rules]

You can use a mityvac to both suck or blow fluid, so can be used to reverse fill as well. I bought a mityvac for use on cars for one man bleeding - but to stop air being sucked past threads you have to either put teflon tape on threads of nipple or another way I found (on cars) is to take nipple out and put a couple of fat 'O' rings around the thread (they end up between caliper face and the slight shoulder on nipple where hex meets thread), when you unscrew the nipple these act as a seal to stop air getting into fluid you are sucking out, and also when nipple tightened down they seal off the thread area from water and other crud.

[Bibio]

been using PTFE tape on nipple threads since the 80's. you need to know which way to wind the tape on or it all just bunches up as you put the nipple back in. PTFE tape serves two purposes, one is to seal the threads to stop leaks and the other is to stop the threads from seizing.

never thought about using o'rings.

[Blapper]

simple. with a large bubble you have fluid either side of the bubble (large bubble makes up a chamber) and when you pull the brake lever the fluid above gets compressed then compresses the bubble which gives less compression of the fluid below. with lots of tiny bubbles you have fluid surrounding the bubbles (no chamber) so gives a direct path for the fluid to compress. the tiny bubbles still compress so gives less performance than no bubbles.

another thing (especially so with curvy rear brakes) is to crack the banjo bolt at the MC on the pull then close just like bleeding at a nipple. its know for air to get trapped at banjo bolt unions more so than in the lines.

best thing to do is let the braking system settle in then do a second bleed.

if you dont have a proper bleeding kit and just using a tube and jar you must make sure that the tube at the jar is submersed in fluid or you will draw air unless you do the 'pull,open,close' method on the lever/nipple.

always have a bucket of water and a wet rag handy when bleeding brakes, brake fluid is hygroscopic and water neutralises/dilutes it enough not to cause damage to paint if you have a spill.

Doesn't work like that I don't think - pressure acts on the bubbles from all directions?

[SV650rules]

been using PTFE tape on nipple threads since the 80's. you need to know which way to wind the tape on or it all just bunches up as you put the nipple back in. PTFE tape serves two purposes, one is to seal the threads to stop leaks and the other is to stop the threads from seizing.

never thought about using o'rings.

I bought an 'O' ring kit from Halfords, ( HBB131 ) and ones I use are 3mm x 12mmOD x 6mmID and 2.5 x 11mmOD x 6mmID (but for car nipples).

I always found the best way to apply teflon tape is to miss the first couple of threads (otherwise the tape extrudes out and you end up with a spiders nest of tape on the inside of where you are screwing into) and then hold tape unto thread with thumb and turn fitting clockwise as though you are screwing it into hole (stretch tape as you screw), that way when you actually screw it in the rotation tightens the tape into thread rather than trying to push it off.

I learned a long time ago (the hard way) not to use teflon tape between a rough and smooth thread when I replaced all radiators in house and used teflon tape between male chrome fittings and female radiator threads (which are normally very rough finish) - well the rough thread just tore the tape and every one leaked, I redid using RTV silicon gasket stuff and not one leaked.

[Bibio]

Doesn't work like that I don't think - pressure acts on the bubbles from all directions?

only small bubbles. when you apply pressure the brake lever you are creating a closed system, the brake fluid then acts like a solid of sorts. anything in the system with less viscosity will compress e.g. the trapped air. if the trapped air is a large pocket with no fluid around it then the fluid will compress the air instead which in turn gives less pressure to the fluid below. air is easily compressed and this results in more travel at the lever.

the sv brakes are not bad, its just that people dont service them properly so complain of poor performance. they then try all sorts to improve then like fitting braided lines instead of addressing the real issue as most people think that they dont have the skill to do so or are scared that they will mess things up. in reality servicing callipers is easy once you learn.

[aesmith]

.. I don't understand how loads of small bubbles gives a less spongy lever than one big one, but it does work. I was sure it was BS until I tried it!
Probably because there's less actual air. 1000 bubbles of 1mm diameter have the total volume as one of 10mm diameter.

[Blapper]

Hmmm, I think fluid slides around the air (is 'fluid') and so pressure acts in all directions. Only the pads on the discs, the M/C piston and the brake lines contain the pressure. The volume of air in the system givse an amount of compliance which the size of the bubbles can't change as the total volume of air is the same. No, I think there is something going on that we both don't understand because it does give a firmer lever, like you said. Bizarre!

[SV650rules]

I agree with Blapper on this.

Maybe when the air bubbles are left under pressure for a long time some of it gets absorbed (goes into solution in the fluid) by the fluid like nitrogen in a divers blood or CO2 in a fizzy drink, we know brake fluid is hygroscopic so maybe absorbs hydrogen and oxygen from the bubbles as water ? Or maybe it is easier for smaller bubbles to find their way back into reservoir before they can expand again.

Or maybe the air, being the least viscous stuff in the master cylinder can actually get back past piston seal and up into reservoir when system is left under pressure.

[johnnyrod]

Can do - leave it on full left lock i.e. the master cylinder banjo bolt is pointing bolt-head down, so the bubbles collect at the m/cyl end. When you release the cable tie they'll suck into the reservoir. It also pushes the brake pistons out for a long time, so if they have been sitting back a bit in the calipers (which causes excess travel) then they'll get used to being in the right place.
Like I said... in regard to tying the lever overnight. The small bubbles need time to collect (they rise slower than large ones), and they need a way out. Also caliper pistons sitting back causes excess travel as you waste some lever stroke just getting the pads to the discs.