can someone tell me how to bleed my front brakes on my 80 ironhead. I replaced the master cylinder with a new one, filled it with fluid and tried to bleed it and am not having any luck. I have a single caliper set up.

please explain it to me like i have never seen a wrench before because i am doing something fundamentally wrong.

I tried using my small hand vacuum pump and got it to pull a small amount of fluid through but not much.

also tried doing it the more traditional way and got no where

 

bench bleed the master first?

 

I assume the lever is soft? Turn your handlebars so the MC is as level as possible. Fill MC and pull lever back to handlebar and tie off with a zip tie overnight. Cut off zip tie. Try to bleed after setting overnight, it will likely bleed well.

 

1. What I had to do on my 1980 was to dismantle each line at both ends and blow spray can brake parts cleaner thru the lines, especially thru the 3-way connector under the steering stem.

2. This is not mine but it works for another forum member ...
I turn the front wheel all the way to the left so I can fill the master cyl. as full as possible (WITH SILICONE FLUID), let set a few minutes then open the bleeders on both discs until I get a steady drip of fluid, then close them.

Then I pump the brake SLOWLY several times until I feel a little resistance in the lever. Wait a minute then it pumps up to to nice hard feel. Works every time.

3. I'll try to post more info tomorrow

 

here is what i have tried

I filled the master cylinder up and put a plug in it and pumped it slowly untill it was nice and firm, some bubles coming out the top of mc when i did this and the lever felt good

then i put master cylinder on the bike

disconnected the line at the caliper, blew conpressed air thought the line and it was coming out good, the line goes from the mc to the TEE under the lower tree, the tee has a plug in one side and then another line goes to the caliper, everything seems to flow good through here

i took the caliper off and took the bleeder off and blew air back and forth between the line hole and the bleeder hole, seems to flow fine

put the caliper on the bike and push fuild through the bleeder untill it comes out the hole for the line, with a little sriringe type thing with a hose on it, this took alot of pressure but it flowed though, but mostly it made a mess

put it all back together and try bledding it and doesnt seem to work

so i have the bleeder closed with the mc cover off and the lever tied down and i take some time to clean the shop because it is a mess.

now i release the lever and slowly pull it a bunch of time while tapping on the line and fitting and bubbles are coming up but it is not building any pressure

I do this routine 1/2 dozen times with a few minutes in between and bubles are coming up each time but still no pressure

 

here is how i am trying to bleed it , maybe doing something wrong

mc cover off
pump the lever several times, hold lever down, open bleeder, close bleeder, release lever

repeat

when i do this fluid is coming out of the bleeder, then i close it before it stops flowing out

 

sometimes a bithc to bleed from dry!!!

try the gravity method........ya gotta keep an eye on it......but .......
Put a hose over bleeder valve to another container

Fill MC..........
open bleeder valve.......
let it sit for awhile.......let gravity get some fluid down the line.....you should see fluid in hose to the container.......
refill MC as necessary....once you feel confident there should be enough in the line......
close bleeder and try the pump/open bleeder/close bleeder process.

 

well it finally worked
I just left the level tied back and would go joggle the lever and pump the brakes a few times, then all of a sudden it just started pumping up. from there it bleed just fine

 

This is the technique that I have used. I use a 60 ml irrigation syringe purchased from a home health supplies store, and a short piece of very tight fitting clear tubing. If it took a lot of pressure then I think there was a blockage in the line or fitting. It seems to have cleared up

 

Your welcome, ref post #3