Air bubble in the brake fluid resevoir....

illusion · Scooby Slapper Joined: 04 Apr 2005 Karma :

...is this a bad thing? Does it need sorting?

simon1221 · World Chat Champion Joined: 28 Jul 2004 Karma :

Do your brakes feel spongy, ineffective?
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Hex · Party Boy Joined: 04 Feb 2002 Karma :

Its just where the fluid has taken up the space from where the brake pads have worn.

As long as the amount isn't too low I wouldnt worry about it.
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illusion · Scooby Slapper Joined: 04 Apr 2005 Karma :

Yeah my brakes aren't great. They could probably do with new brake pads actually though... But the fluid is way above the minimum level

Guest · Brolly Dolly Joined: 22 Apr 2004 Karma :

So are you saying that there's a good level of fluid in the res, but there's a bubble in there as well?

If it's not coming up to the top then it's not air, I'd say it's probably water - needs a serious coat of looking at.

Finglonga · World Chat Champion Joined: 27 Jul 2004 Karma :

Don't Panic... If there was water in there you would know about it as the fluid soaks up water like a sponge and your brakes would not work!

You will have a max and min mark on your reservoir as long as the fluid is between these marks you are O.K.

You cant see bubbles that make the brakes spongy as they are in your lines, try pulling the brake lever fully on and tie it there overnight, next morning you will find the brakes alot better as the air bubbles (if you have any) will have risen to the surface.
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easy · Derestricted Danger Joined: 09 Jul 2005 Karma :

Guest · Brolly Dolly Joined: 22 Apr 2004 Karma :

Or are you saying you can see a 'bubble' in the level window? That's ok, shows there's fluid in there

https://www.bluepoof.com/motorcycles/howto/nighthawk_brakepads/reservoir.JPG

Kram · World Chat Champion Joined: 20 Oct 2004 Karma :

both my front(braided) and rear(rubber) brakes feel spongy? and on the front i have to pull the lever along way in (adjusted fuilly out).

do i just need to bleed?
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easy · Derestricted Danger Joined: 09 Jul 2005 Karma :

Kram · World Chat Champion Joined: 20 Oct 2004 Karma :

how hard are brakes to bleed?

how long does it take? any 'special' tools needed?
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FS1E -> SR125 -> CB400N -> CB650 -> FZR600 Genises -> VFR400 NC21 -> CBR900RR Fireblade -> Renault Clio 1.4

Finglonga · World Chat Champion Joined: 27 Jul 2004 Karma :

easy · Derestricted Danger Joined: 09 Jul 2005 Karma :

Or Google Bleeding motorcycle brakes . Although this could find someone who isn't happy with the brakes on their bike. Laughing

I found this and this were usefull, but if you want to get precise instructions investing in a Haynes may be better.

As Finglonga says it's fairly straightforward to do and after you've done it just give it a few 1st gear hard stops to make sure there's no problems and then go easy on the braking for the next couple of days. Like I said above not being able to stop on a bike is not fun, so a couple of days should show if there are any long-term problems.

If there's air getting back in again, then it's time to service the calipers, lever/pedal and maybe replace the lines, just for overkill.

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Bleeding brakes is not difficult (although bleeding an empty system can be a nightmare).

However on the FZR you have a standard Yamaha brake system, so the calipers are probably the problem. If they are spongy they chances are you need to clean the calipers out thorough, especially behind the seals. Possibly replace the seals as well.

By the way, the only common fluid that does not absorb water like a sponge is DOT 5 (notDOT 5.1, which is very similar to DOT 3 and DOT 4), and it is very rare to find that used. Does seem to get used on older vehicles that are doing a very low mileage as you can pretty much just stick it in the system and forget it afterwards (does not absorb water, so that is the main reason for replacing brake fluid out of the way). However it is a pain to use properly as you need to make sure every trace of water is out of the system, as otherwise the water will settle to one point in the system, boil easily causing spongy brakes when used hard, and cause corrosion.

All the best

Keith
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