Master Cylinder leak??

[Minirider22]

Hey guys Im brand new to th forum and would really appreciate any help, thanks!!

Ok so to start off, I got a chinese pit bike for my girlfriend, problem was the brakes didnt work. The guy I got ti from said they just needed to be bled. Being a very gullible person, I just nodded said alright and continued on home. I got home to realize the window on the front brake master cylinder was broken out and thy replaced it with some sort of gunk, which of course, didnt hold up. When I hit the front brake it just poured out of a little pin hole. I went down to the hardware store and got some JB Weld. and put that on, then to the back brake... I noticed the rod comming off the brake peddal itself was going into the master cylinder at an angle, I refilled it, and tired pushing it, no luck, some did run down the rod but not much. I then took off the hose, going into the caliper, pushed the brake, and fluid shot out. Now Im stumped.
Is there something wrong with the caliper? cylinder? both? Im not really sure how to check or trouble shoot the problem. also when the jb weld dried up, i filled the fluid, bled it, and it also, did not work. and I almost forgot.. the back brake seems like its always a little engaged, without hitting the brake, and when I do hit it, nothing happens.
Appreciate taking the time to read all this!

 

[rotn50]

Welcome mate. try this on the rear. They can be a bugger mate. Pull the hose and resorvoir cap off the master cylinder and the hose off the caliper and remove bleeding nipple on caliper also.
Fill both sections on the resorvoir with fluid and fill the caliper with fluid also(both holes)and replace and lightly tighten the bleed nipple only.
Install the hose on the resorvoir and tighten, do not put cap on the resorvoir so you can fill it with fluid.
Hold your fingers over the caliper end of the hose and make a good seal(with fingers, keeping the hose higher than the resorvoir), as you push the brake pedal down you want to let your fingers loosen slightly letting air out of the line(do this process in between pushing down and reaching the bottom of the pedal, as you dont want to suck any air in)
When you start getting fluid coming out and whilst bleeding the line and starting to feel pressure you may keep your fingers tight on the end of the hose(keep an eye on fluid level and fill accordingly), when pressure is at a maximum you will not be able to hold the hose(keeping fingers tight)without fluid escaping due to full pressure, whilst pushing on the brake pedal.
When you feel this has happened, install the banjo bolt on the end of the hose and quickly install on the caliper.
Your line should be 99.9% bled, check all fittings are tight and that the resorvoir is full and install resorvoir cap. 
Pump the pedal and prime the caliper until you feel the brake pedal stiffen and move the wheel with brake on to check functionality.
If your happy with the brake then leave it(only if your brakes are locking with you sitting on it and moving back and forth), if they are a little spongy you can then bleed like a car brake system, or if all has gone to plan you can crack the bleed nipple(remove resorvoir cap for filling) and the fluid should run(gravity bleeding)and some air bubbles should be present at the nipple, but if you get brakes and think there good leave them, not all brake system bleeds are this complexed but for no reason some are an absolute nightmare, this sounds like your prob.
With the front if you bled it, have you tried to keep pumping the brake lever to prime it?

 

[THUMPINOZ]

Sounds like your brakes are pretty much stuffed at both ends, Hope you got the bike cheap?

Post a pic, (what type of bike) That would help, We can see what brakes you have then

By the sound of it (If they are leaking) you will need something like these to fix it>

FRONT BRAKE MASTER CYLINDER Pit Dirt bike, Thumpstar 70cc 110cc 125cc 140cc | eBay

PIT BIKE REAR MASTER CYLINDER THUMPSTER ATV 140cc 160cc 250cc ATOMIK PIT PRO | eBay

master cylinder pit bike | eBay

Just make sure they match up or the measurements for the rear master cylinder have the same rod length