new to this and having problems diagnosing my front brake problem (Part 1)


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hey guys my names jon and im pretty new to the whole maintenance thing, i own a 1979 xs400, and I'm 22. ive been riding dirtbikes, quads and dunebuggies since i was 6 but never really had to maintain anything seeing how the toys i used werent actually mine and they were relatively new. im pretty savy with tools and i know the jist of just about how everything works but I'm lacking in experience... my goal for the future is to change it to a cafe racer but right now main priority is getting it running safely and learning how to do it on my own anyways here goes...

so after storing my bike in a family friends backyard before moving to florida for a while, i recently recovered my bike. it was sitting there for a year and after being hit by sandy in long island, ny the cover was blown off and was exposed to the elements for the past like 9 months. besides the fact that shes a lil rusty and needs basic maintenance shes still intact...
anyways i got it back and upon turning the key i found i still had battery life not much but i knew it had enough to start it if it didnt have any water damage... after about maybe 2 kicks i realized this baby was fine in terms of engine damage and i knew she'd start up.... 20-30 kicks later she starts up sounding just as i remember and after running for about five minutes she ran on her own without any riddling with the throttle... so i bring it to my step dads friends place to store it he says hell fix whatever needs to be done to get it running safely on the road as long as i get the parts... i pick up new wheel bearings, new oil, brake pads, air filters, fuel filter, new gas, new chain, new spark plugs, new battery, and a couple other little things. so three weeks later due to bills and whatnot i finally go to this guy and nothings done except he sprayed the bike down with wd40 and wire brushed it a bit so the rust is mostly gone... i live in brooklyn btw, but my bike is still in long island and until i can get it back to my house its sitting outside my friends house till its safe enough to drive back and i can only work on it outside when the weather is permitting and obviously only during daylight besides juggling my work schedule..... so yea continuing the story i went to long island and was there for three days, i managed to install all my new parts, and the bike is running beautifully, im so happy for that considering what it went through.... but i realized after riding around the block a couple times that the front brake wasnt what it used to be so i decide that before i even attempt to ride the bike back home where i can work on it in the freedom of my garage, i need to make sure theyre working tip top...

this is where my inexperience really shows,
so i figure that the front brake probably needs more fluid and to be bled.
always in the past i thought that the black seal in the top of the reservoir was the reservoir. wow im an idiot.... so i fill this thing and i try to start bleeding the brakes by unscrewing the bleeder and pumping the lever till fluid starts coming out of the hose i attached. about a tablespoon of gluid comes out and then i mustve sucked some air in cuz then the pressure was released... so i go further into this reservoir and i realize that that seal wasnt the reservoir and underneath it theres a crap load of brown gunk and like little rust balls that look like brown breadcrumbs... it fill more fluid and try to bleed again after some research in the forums, start pumping, loosening bleed screw, pumping then holding brake, while holding closing bleed screw. as im doing this im looking into the reservoir and the level is not dropping i see no air bubbles, nothing, with bleed screw open and closed...... so i suck up all this crap clean the reservoir take it off then i find the two holes in the bottom, i realize this is where the fluid goes through the master cylinder to go to the hose etc.... so i decide im not messing with this thing until im sure that its the master because i dont know shit about this clearly... so i go down to the caliper, find out that it might be seized i see some corrosion around the piston and i figure that since i cant push in or pull out with my hands its seized... more research.... i push it in and get it to come out, not easily but it does move in and out, however i may have damaged a bit of it , not around the main part that creates the seal with the caliper, but more around the part that goes inside the seal.... 1) idk if its because this might be seized that no pressure will build but yea.... anyways after feeling comfortable that its not the main problem i start disecting more.... i know this probably sounds scary but its the only way im really going to learn how to deal with this in the future, worst comes to worst i buy everything new, not trying to do that yet i detach the brake line and i blow through it , i hear air flowing through both sides and no rust particles coming out so i figure its not the line.... i reatatch the line only to the caliper and i blow through the top end, i hear and see fluid and air come out of the bleeder screw so i figure it cant be that theres a clog... more dissecting. im at the master and reservoir again and dreading it. i have no pump or vacuum or anything to suck out the debris i see in the holes that lead into the reservoir so i put my finger in the hole that the brake line is connected to and after ive taken off the plastic reservoir ive put about an inch 1/2 of fluid so theres no air coming out of the holes, then i pump the brake, rusty pieces start coming out of both holes... its gotta be this damn master cylinder. my finger is starting to hurt from the pressure so i take it off, im guessing now theres air in there now cuz as i pump i see some bubbles, but i feel like the fluid coming out of the holes just isnt enough, its not squirting out and making a mess, only just these tiny tiny bubbles... so my friend upon telling him its probably a bad idea, says why dont we try wd40 to force out this crap.... i really hope this wasnt really bad for it but im desperate at this point knowing that this is the only thing stopping me from riding after being foot bound for over a year... so i try it, same method but i spray the wd40 into one hole, lots of more shit flys out, do it to the other hole, then clean everything and add more fluid.... id do this about 10 times feeling comfortable that there isnt much left if any at all, so after a good cleaning, i reattach the brake line, fill the reservoir and pump i notice that fluid is coming from the line now but still it just doesnt seem right.... forgot to mention that i tried this before to see if there was i clog in the line and there was only a very small drop of fluid coming from the line possibly i couldnt really tell but if any it was just like a miniscule drip, i figure it would be like a water gun and squirt a lot of fluid considering that this is all pressure based and a little drip wouldnt create enough pressure to push this piston, and im hoping this is the issue. ..... 2nd problem) when i pump the lever and theres alot of fluid in the reservoir shouldn't alot of fluid come out? or as long as there is fluid coming out pressure can be built after all the air is released by pumping vigorously and bleeding by pumpingg alot releasing the bleeder screw, holding the brake while simultaneously closing the screw and doing this repeatedly for hours will eventually get enough fluid in the line to force out the air, bleed properly and return pressure? (sorry i know that wasnt phrased well but ive typed alot and am losing my place) theres a part 2 cause this is so long sorry:(.........
Before you type up a second part to this, I just want to summarize the situation to make sure I follow.

1. You've blown compressed air through the brake lines as well as the caliper. Good! We can be sure there isn't a block there.

2. Before you do any more bleeding, make sure all the gunk from your reservoir has been cleaned. Your master cylinder is very sensitive and is easy to damage if it has been exposed to rough materials. This includes the little rust balls (and brown jello I have found in mine) and the cylinder bore itself. If the master cylinder piston is pushed beyond its normal travel in the bore, seals inside can tear. This is why brake bleeding can take a great deal of time. Small steps and LOTS of cleaning.

3. You noticed some damage on the caliper piston. This can cause a drop in pressure. If you can detach your caliper from the bike and get it on a bench, you can easily pop out the caliper piston and inspect it for wear. Do not remove the piston with anything sharp, because you WILL damage your piston and have to replace it. Once the piston is out, clean it off with brake fluid and inspect it. If you notice any pitting or scratches on the outside, you have found where a drop in pressure may have occurred. You can try to buff it out with 2000 grit sandpaper and clean it with brake fluid again. If it still looks damaged, it will have to be renewed.

4. Your brake system only cycles a small amount of fluid and is not always dependent on how much fluid is in the reservoir. So long as all other conditions are equal, a full reservoir and a half-full reservoir will pump the same amount of fluid. Your caliper piston only needs to move a millimeter (if that) to engage your brakes.

Note: WD-40 isn't a good decision for the future when working on your brakes. Brake fluid is a hygroscopic fluid (meaning that it absorbs water). WD-40 is a water-based penetrant. It's not as bad as using something like Liquid Wrench (which is petroleum based and will destroy the rubber seals in your system), but from here onward I'd suggest simple compressed air to free it up.

When I bled my old fluid, I noticed that there are two small tabs on the inside of the reservoir. I assume they are used to pull out the reservoir if needed. One tab, however, can get stuck over the holes in the master cylinder and recycle air bubbles that are forced into the reservoir via the fluid return hole back into the fluid intake hole. Turning these tabs 90 degrees can free these air bubbles and allow you to bleed the system.

Hope this helps! :)

Also, welcome to the forum!
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Thanks alot for all the advice man it really helped... I figured out the master cylinder was just pretty much done for, new ones on its way