Brake Issue
 

So im working on my little brothers yz85 and need some help. To give you some back ground the master is a standard amster, i just rebuilt it. the caliper is a 2 piston floating caliper, and the line is good.

The problem is that the brakes wont work. I have bled the lines and nothing, rebuilt the master-nothing.....I did install a "shindy" master (old one from my big bike) and it works but not as good as what a stock master is.

Baiscally there is no pressure at the lever (properly bled) but it squeezes the caliper, just not tight enough. When it squeezes it also moves like it should but it moves the whole damn rotor.

I haev no idea what it could be, my next step is rebuilding the caliper but i dont want to spend the money and it be a waste so if you have any thoughts lets hear them.


Thanks

Re: Brake Issue
 

A streetbike master is too big for a yz 85 rotor and caliper.

Re: Brake Issue
 

if the rotor is moving then the caliper is either not sliding or if it has one piston on each side then one is not working ..

if it has two pistons on one side then the caliper is not sliding and you will need to clean and lube the slides

Re: Brake Issue
 

sounds like a master cylinder, try a diff one. if neither work then its more than likely a seal problem in the calipers. The rubber rings that seal the pistons are directional. might be in backwards. thats on ktm calipers thats the only ones i know are like that. yamahaha's may be diff

Re: Brake Issue
 

[quote=SUPERDAVE;4099368]A streetbike master is too big for a yz 85 rotor and caliper.[/quote]

It worked but not as good as a stock one works


[quote=old man roger;4099426]if the rotor is moving then the caliper is either not sliding[/quote]

The caliper is sliding and is able to slide

[quote=repsolstuntin1;4099739]sounds like a master cylinder, try a diff one. if neither work then its more than likely a seal problem in the calipers. The rubber rings that seal the pistons are directional. might be in backwards. thats on ktm calipers thats the only ones i know are like that. yamahaha's may be diff[/quote]


The Master is good now i rebuilt it with the pieces facing the right direction


Did some more investigating and i believe what is causing the rotor to bend (possibly not braking well either) is the inner pad (next to the pistons) is getting caught up on something and when the piston expands out of it cavity it is staying stationary relative to the fork and the actual caliper is moving outward causeing the rotor to warp.

This might be the reason why it wont brake as well because the outer pad will touch the rotor but until it hits the inner pad it wont stop the bike


Is this a possiblity to any brake gurus out there? Because i just finally gained understanding of floating calipers and this was my only thought

Re: Brake Issue
 

if it's bending the rotor then it's not sliding freely:2cents

Re: Brake Issue
 

I got it fixed...The pads were hanging up which was causing the rotor to bend as well as not being able to bleed it fully...

Once i got it fixed its butter