BRAKES-basics

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi all,
never really trusted myself to brakes,seeing as they do quite an mportant job, lol
but recently decided to give it a go, (seeing as i have 2 project bikes on the go,both neding brake overhauls)
i have read a few basic guides & now understand the theory side of things.
here goes, front brake for this bike was supplied off the bike. in a box, lol
came complete, almost.
its a single caliper, with 2 pistons. & i have cleaned it all up.
pistons & seals are all ok.
but theres no brake fluid in it yet.
whats the best way to get fluid from the m/c, at the lever end, down to the caliper?
that may sound like a stupid question, but as the complete brake is not on the bike, im wondering if i should do it differently?
puting brake fluid into the reservoir is easy enough (now that i have dremelled the screws out!)
but actually getting the brake fluid down to the caliper seems to be a bit of a problem.
gravity doesnt seem to help, as i tried putting the brake lever higher up than the caliper, with the bleed nipple out.
but when i pump the lever, nothing comes out at the bleed nipple!
can someone point me in the right direction?
i have had a look at the guides in here, but none of them tell you how to fill a brake system from the beginning, only how to change fluid.
i understand the principals are the same, but some advice would be welcomed!
sorry for rambling & hope it makes sense! lol
cheers,
GAZ

hmmmnz · Super Spammer Joined: 22 Aug 2006 Karma :

i would buy a siringe off ebay, and fore the fluid from the caliper up the lines to the resivoir, forcing the air bubbles up:D
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Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

From empty it can be a pain. Several tricks.

Get a vacuum bleeding kit. Connects to the bleed nipple and then it sucks the fluid down.

Fill from the bottom. Get a large syringe, fill it with brake fluid, connect it to the bleed nipple and push the fluid into the system up to the reserviour.

Take off the brake hose at the caliper. Put the end into a pot of brake fluid and pump the lever. The pot of fluid acts to stop it drawing air in. Can work to get a bit of fluid in the system and get things started.

Fill the reserviour with fluid. Pull the lever a tiny amount (maybe 5mm) and release. Keep doing this slowly. Idea is that tiny bubbles of air will come from the master cylinder into the reserviour (tiny hole in the master cylinder, not the larger one). Only need to pull the lever a tiny amount as after that the piston covers the hole.

Once you get some fluid in there you can start to bleed it normally.

All the best

Keith
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stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

Hi,
thanks guys.
didnt really fancy spending ages pumping the lever trying to get all the air out & fliuid in!
gonna try the syringe method.
off to ebay...
cheers,
GAZ

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi again,
still trying to get brake fluid into the caliper, & seeing as i have the time, but no syringe, i thouight i'd keep at it.
got brake fluid in the m/c, hose & caliper, but obviously have plenty air as well, which i will attempt to bleed out.
but one problem i've noticed, is that i have a leak!
firstly, i havnt split this caliper, as the bike came with one loosely fitted to the bike & 1 in a box.
i was under the impression that the one that was on the bike is ok, just needing pins, pads, clips & shims (i have the pads, pins in the other caliper i cant get out, so will probably have to buy replacements) & re-filling with fluid.
anyway, there is fluid leaking out from where the 2 halves join together, when i pump the lever.
so i split the caliper, just to have a closer look.
i've checked the on-line parts fiche at cmsnl, but the pic is crap & the list makes no mention of an o-ring.
but am i right in thinking there should be a small o-ring in the indent?
(top left in pic)
there isnt one in either caliper, but im thinking there should be, can anyone advise?
cheers,
GAZ
EDIT - sems im right, there should be an o-ring there, according to workshop manual.
thing is, i used to have loads of different sizes of o-rings but not many left & seen a box at the market yesterday, was only about 3 or 4 quid, picked it up but put it back down again & decided to buy nut & bolts instead, doh!

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

There should be a flat rubber washer there. Be careful about using a random rubber O ring unless you are sure that not only does it fit but it is made from a material that will not be attacked by brake fluid.

Some makers do not list those rubber washers as spare parts (ie, Yamaha don't seem to for lots of bikes) while others do.

By the way, what bike is it? I had assumed it was the VFR, but they use twin pot sliding calipers rather than opposed piston calipers (I think).

All the best

Keith
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stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi,
its the front brake off the rg125 gamma.
sorry i should have mentioned that earlier, oops!
but your right Keith, (as usual,lol)
the vfr has twin pistons, whilst the gamma has opposing pistons.
looks like im gonna have to start from beginning!
got fluid into the thing, but it was also leaking from m/c!
sorted that, the diaphram needed replacing, had a spare. (dunno where the hell that came from! lol)
& fluids getting into the caliper, as i can hear it gurgle when i open the bleed nipple.
but the pistons arent moving!
i should really have checked that first! doh!
looks like thats 2 brakes needing stripped down!
(the rear on the vfr, which has been in bits for months! & this 1 from the gamma)
guess i shouldnt have beleived the seller when he said "it just needs the pads fitting, with new pins & spring/clips"!)
there definately wasnt any rubber washer or o-ring in either of the calipers i got with the gamma, but i hadnt thought of it being made of any special material, oops.
as i did find a random flat rubber washer that fitted nicely & its now sealed.
gonna go blast the pistons with the compressor!
cheers,
GAZ

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

If there is loads of air in the system it is easier to compress the air than move the pistons. However if they are appart then worth popping the pistons out to clean things up and check they are OK.

Think Suzuki normall do list those washers. Quick look at some Bandit calipers on a fiche and they seem to be sold as part of a seal kit for the caliper.

All the best

Keith
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stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi,
given up for now.
pistons seized.
managed to get 1 out with the airline, but the other 1 wont budge!
seem to have problems with brakes, thats the vfr & thr gamma both had seized pistons, due to inactivity.
but the gammas a priority, seeing as its the missuses christmas pressie!
time to admit defeat & take it/send it to someone with a brake piston removal tool.
someone who knows what there doing could probably re-build it in 20mins!
its took me all afternoon & i havnt got anywhere! lol
cheers,
GAZ