[Urgent] How to bleed speedfight 2 brakes.

[dameize]

Hello All,

My rear caliper went on my bike the other month and I havnt had the time to get it sorted. Usually my granda is the one that does this stuff (im 18) and I tend to help a bit and learn from him.

Anyway, the rear caliper has now been fitted and is fitted correctly and we have bled the rear brake and it half works. It is only mediocre though and clearly needs doing more.

My question however is on the master cyclinder there is a rubber insert that had fluid in it but there is no holes or anything so i dont get how the liquid leaves.

Do we put liquid in area under the rubber insert and in the rubber insert? or just one of them?. At the moment we have liquid in both. We filled it up and then put the rubber insert backin and filled that and like I said it works but its not very good at all.

Any advice would be awesome as we were going to redo it tomorrow but are a bit unsure.


Thanks.

[Tuffers]

after you have bled it and topped up the master cylinder you need to carefully roll the rubber diaphragm from one side to the other when you put it back in or else you will get air trapped underniegh

any air trapped would make your brake feel spongy and not that powerful

also make sure you havnt already spilt oil on the disk/pads cause that can stop them from gripping

[dameize]

do i need to fill up the inside of the rubber once i put it over it?

[Tuffers]

No the rubber is only there to make it an air tight seal

[dameize]

could filling the rubber up be the cause of it not working right?

[Tuffers]

it is most likely not bled properly or you havnt put the rubber diaphragm in correctly causing an air pocket underniegh

This video is for mtb hydraulic brakes but is pretty much the same for your pug
https://blip.tv/play/gpkd4J1dAA

[andys675]

you'll never bleed it properly, you have to feed it backwards from the caliper with a syringe, believe me, I used to work in a peugeot scooter dealers

[Walloper]

The rubber is there to prevent foaming when the fluid is agitated when the bike is moving.
To fill you need to remove the rubber and fill to the mark.

Bleed form the calliper or from the master cylinder.
Some folk prefer the 'backwards' filling.

Not easy to find a big syringe so I use the 'Normal' way by filling the reservoir and pumping the lever.

It takes a long time to do this as the master cylinder piston is small and the travel is short. Persevere and allow some time for fresh fluid to run/bubble into the master cylinder after each pump.
There are various techniques some say you pump fast several times then slowly and then with the lever pressed down open the bleeder.
I have tried this was and found it made no difference.

Ensure the master cylinder is full. If that is not full it cannot pump much or the full amount of fluid which will make it even more difficult.

With the lever down open the banjo coupling connecting the hose to the master cylinder and let any air out.
Close the couling and let the lever up sloooooly.
Let the master cylinder refill and repeat.
Do that until you are sure the air is removed then go to the calliper.

Same as before pump the lever down and hold it.
Open the bleeder screw.
Close the bleeder.
Let the lever up.
Continue.

Back brakes are 'normally' easier than front brakes as the level of the cylinders promote better removal of air.
Fronts brakes have the master cylinder away above the calliper which doesn't help.

I use a Gunsons pressure bleeder thing where you fill the bottle then put a little air pressure from a tyre into the bottle.
This pressurises the fluid which is then 'pumped' by this pressure into the master cylinder.
You do not need to pump then as the 'tyre' air in the bottle pushes fluid and trapped air out the system.
This gives a very firm feel of the brake levers too.
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