Tip when bleeding brakes

[squishio]

Last time I tried bleeding my brakes I failed and the brakes just felt like they were full of air.
So I ended up taking it to the dealers to get it done.

I thought I would try again this weekend.
So I fitted my new pads and then went about flushing the system of old fluid.

I got some out but the lever just kept pumping and not getting harder.

I spent a good 45minutes trying to figure out where I was going wrong.
I had topped up the reservoir and replaced the cap before I started pumping. Big mistake was replacing the reservoir !

So whilst pumping it was creating a vacume in the system and not pushing out any fluid or air. As soon as I took off the cap the lever almost instantly went solid


So lesson learnt - Leave the res cap off whilst bleeding brakes !!!!!



Prior to doing the brakes I bought one of these...

https://cgi.ebay.co.uk/MOTRAX-LITTLE-BLEEDER-MOTORCYCLE-BRAKE-BLEED-KIT_W0QQitemZ180313165592QQcmdZViewItemQQptZUK_Motorcycle_Parts?hash=item180313165592&_trksid=p3286.c0.m14&_trkparms=72%3A1689%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318


What a fucking waste of money!

The valve is not completely tight so fluid still goes back down the pipe.

But even worse is that when I undo the bleed valve and start pumping the fluid leaks up around the valve thread, So if it is leaking out then I guess it is also sucking air in.

So I ended up opening and closing the valve manually

Does anyone else have this problem?

I was not releasing the valve very much, just enough to break the seal to let fluid out.
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Current - Hornet 600, Transalp 650, X140 Pit, GPZ400R
Past - SY125, GT250, GT650, CX400, CBF600, Bandit 600, SL1000, GT250

[Mark65]

Hi
When i did my changed the fluid on the front brakes on my ybr i just used the old style 1 way valve from halfards for a fiver, run it into a plastic container with some fluid in then raise the container and tube or at least the tube above the bleed valve then when you pump the brakes all the little air bubbles will rise away from the valve,where as if it is lower they will rise back to the caliper.

But i would like one of these:
https://www.workshopsupplies.co.uk/index1.html
They do a plastic one as well for about half the price.

Mark

[Kickstart]

[squishio]

Sorry yes, Keith you are exactly correct.

The rubber diaphragm was fully extended, as when I first started some fluid was pushed out but then it stopped presumably when the diaphragm had been sucked down.
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Current - Hornet 600, Transalp 650, X140 Pit, GPZ400R
Past - SY125, GT250, GT650, CX400, CBF600, Bandit 600, SL1000, GT250

[loply]

Incidentally, by far the easiest and most effective way to bleed, as well as the cheapest (and also the best way to refill an empty system) is using RFI (reverse fluid injection) and a syringe.

Go on ebay and buy a 100ml plastic syringe, and get yourself 20cm of clear plastic tubing (B&Q sell it).

Slide the tube over the syringe, fill the syringe with fresh brake fluid, squirt the air out and then squeeze the fluid into the bleed nipple on your caliper.

The resevoir at the top will slowly fill up and the odd bubble will appear.

Do this for 10 mins and voila! Just be careful as the resevoir will fill up and require periodic emptying as you go...
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Yamaha SZR660 Caution to the wind, the throttle pinned!

[squishio]

what about the air in the top of the caliper around the bleed valve?
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Current - Hornet 600, Transalp 650, X140 Pit, GPZ400R
Past - SY125, GT250, GT650, CX400, CBF600, Bandit 600, SL1000, GT250

[Wafer_Thin_Ham]

[squishio]

but it's the highest point of the caliper and the syringe isn't going to push all the air out in one go.

So if you have got the syringe attached no air is going to come out that way and the injected fluid is not going to suddenly push the air down and then up the brake hose is it?

I can't say my knowledge is great so I may be wrong but common sense tells me that the air will not be pushed down.
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Current - Hornet 600, Transalp 650, X140 Pit, GPZ400R
Past - SY125, GT250, GT650, CX400, CBF600, Bandit 600, SL1000, GT250

[stirlinggaz]

[salty21]

is it common practice to use the same syringe for for sucking the old fluid out the res? and if so would you need to suck it dry after each syringe full of fresh to make sure the system is using as much new fluid as possible without stripping the calipers.

on a side note, i noticed on my bike that during hard riding/braking the brake lever will sometimes pull all the way to the handlebar and not slow me as much as i want, which is not really ideal

have read a few posts on brake issues and to me it sounds like fluid boiling?? which cant be a good thing.
If so is this usually caused by the fluid being contaminated with water?
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04 NSR 125(sold) ---- 03 CBR 600rr(sold) ----90 pan euro ST1100 '' ----02 CG 125
94 CB400 Super Four ---- 2000 VTR SP1 (sold) ---- 08 ninja p8f(sold, meh) ----05 CBR600rr

[loply]

Contaminated or old fluid will boil more readily than new fluid.

Generally if it boils the brake will pretty much stop working all together, not just become weaker.

Like... the lever comes to the bar, and NOTHING happens.

If you're still getting some action I'd be inclined to suggest it's not that? Either way, flush some new fluid in to be sure...
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Yamaha SZR660 Caution to the wind, the throttle pinned!

[c-m]

i have cleaned up my calipers and installed new pads,. spent ages the other week bleeding my brakes but they are still spongy despite my improved stopping power

[MarJay]

The quickest and easiest way to bleed your brakes is to use a Sealey vacuum brake bleeding tool. But you do need a compressor.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Wafer_Thin_Ham]

[Kickstart]

Hi

I am not sure that I can see how with amost calipers you would dislodge air from the top of the caliper and push it up the hose by pushing fluid in with a syringe. Most calipers there is a bit of volume that will be higher than the entry drilling for the brake hose. Push fluid through the bleed nipple and it is likely that any air trapped there will stay there.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[loply]

If the design of the caliper is bad and the bleed nipple isnt the highest point, then obviouslly you just have to rotate the steering or lift the front or remove the caliper and make it so...

If the designers had any sense though the bleed nipple will be the highest point by a reasonable amount.

Incidentally you make things easier by pushing all the pistons fully in before doing this.
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Yamaha SZR660 Caution to the wind, the throttle pinned!

[norstad34]

Hello all,
I have also tried the reverse method and it works a treat if you have an empty system, I also bleed it normally after I have backfilled it just to make sure, maybe that's just me and my nobrakesaphobia.

[Mark65]

[Ichy]

Absolutely no reason to use dot 5.1, plain ordinary DOT 4 is fine. In fact DOT 5.1 attracts water far more readily than DOT 4 even in a closed system so you would have to change it more frequently.

BTW DOT 5 is silicon based, DOT 5.1 is still polyethylene glycol based.
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https://www.metacafe.com/watch/1972097/how_to_behave_on_a_forum/

[Kickstart]

[Mark65]

I stand corrected on the 5.1 make up but i have not seen any info that says it absorbs more water faster? as i put it in my car, so itchy gets a partial spank lol

Mark

[Kal]

I use DOT4 - not a got a clue what that means but the bike likes it.

I made a brake bleed kit from some petrol tubing and an old syringe - cost nothing, but works nicely. Last time I did the job I back filled it, worked nicely.

I also found that using a cable tie to keep the brake pulled overnight was helpful.
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Kal...
I Like To Hoon It Hoon It I Like To Hoon It Hoon It I Like To Hoon It Hoon It Ya Like To (HOON IT!).
1984 GB250 Clubman,1983 CB250N Superdream, 1999 GPZ500S

[Ichy]

[Ichy]

[Kickstart]

Hi

As far as I can find the wet boiling point is meant to represent the fluids boiling point after exposure to moisture equivalent to a couple of years of use, which is about 3.5% water. Should be a fair margin for error with the wet boiling point of DOT 5.1 being about half way between the wet and dry boiling points of DOT 4.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing