master cylinder

i rebuilt my master cylinder this weekend, and rebuilt the brake caliper because i thought it was locked up. i still could not get the system to bleed, nor could i see the caliper piston move any unless i rapidly sqeezed the brake lever. i took the master apart again and found the rubber cup that sit on the spring was cut. so i put my old cup in, tried again and same issue. took it apart again and it too was cut. apparently the new piston that came with the rebuild kit is flawed, the end of it is sharply flat, smaller, therefore cutting the cup. so i'm assuming that is why i couldnt get the brakes to bleed. should i hit up Chacal for a new cup? get a FZ master cylinder? or get one of these bad boys ebay

 

chacal,never a bad idea but you need a good piston
FZ master is going to be for dual disks
that one on ebay needs the grip removed to put on, what a pain
look on ebay for "usa-motorcycles-inc" they work and their cheaper

 

glad you pointed that out polock. funny you mention usamotorcycles...thats what ive been looking at for the past hour (and the seller is in the same state as me). i eventually want to go with dual disc setup, but that will be way down the road. i dont think using a lager m/c on a single disc setup will be a bad thing, i would just have to get used to the extra bite

 

don't quote me on this one but i think you'll have less bite and need more lever pressure to get the same results
a larger piston has less mechanical advantage, it moves less but to generate the same PSI it needs more lever pressure
if it matters...i don't know
of course i may be FOS won't be the first time

 

ok, so i just did some calculations in hydraulics, and according to what i came up with here are the results: using the stock m/c with a 12.7mm bore will cause 9.3 times the amount of pressure on the stock 38.1mm caliper piston. now with a larger m/c (14mm) it would cause 7.4 times amount of pressure on the stock caliper piston..... so you are exactly right good sir

i didnt know this would turn into a science lesson :lol:

 

now for the unknown variable, i'am thinking a stock MC for dual disks is bigger than 14mm, but i could be dreaming
either one is going to stop you, it'll just feel different

 

i swapped out for a larger m/c on my honda civic one time, but now that i think about it, that was only because i upgraded the rear from drums to discs therefore i needed more fluid.