1977 ironhead front brake issue

[rider7816]

 
Hey guys,,

I have a new to me 1977 XLH.  I just put it back on the road after sitting for about 15 years.  Im having issues with the front brakes.  I have rebuilt the front caliper, new front brake line, and replaced the master cylinder with a new aftermarket unit. Im having issues getting any pressure built up in the lever.  I have manually bled the system about 5 times and vacuum bled the system as well.  It builds pressure and feels great, if I let it sit a minute or so it loses all pressure.  If I pump the lever a couple of times it builds pressure again..

Its driving me nuts.  Just out of curiosity, I noticed that some of the front brake caliper rebuilding kits there is some sort of small spring, my caliper has no spring and I cant see where to put one even if it did..

Anyone have any help with this???

Frank

[Panzer]

There was someone who had an issue bleeding brakes such as yours.
Their suggestion was to clamp the lever to the grip and let it sit overnight.
That way it gets all the air out of the line, if there is any.
Spring??  Can't help you there.
You do have a manual don't you?

[Racepres]

Either yer shiny new ~ MC is Junk, or you have a Leak...If the rebuilt OE MC did the same thing...I'm guessing leak...
What brake line?

[Panzer]

Using the right fluid I assume? 
Just a thought.

[Racepres]

Using the right fluid I assume? 
Just a thought.

Absolutely...Should be dot 5...If Mixed...well you got problems.

[rider7816]

Thanks for all the replies.  Yea, I had to replace the original m/c with a ~ one... I couldnt find and decent factory replacements and mine was unrebuildable.  I definatley used DOT5 fluid as I use it in all my bikes.  The front brake line is a 6" over, ACELL rubber brake line, which was brand new.  I also rebuilt the front caliper and verified that it has no leaks anywhere along with full movement of the piston. 
Im gonna try the gravity blead thing and get back to you guys.

Frank

[HarleyGuy4657]

Try this. Take a large syringe and a short piece of hose and fill the syringe with brake fluid. Loosen the bleed off and attatch the hose and syringe to the brake bleed and fill everything from the caliper up to the master cylinder. The air bubbles want to go up the line anyway and this will push them if any to the resavor . Have had this problem with a dirt bike that I had and it was the only way I could get them to work. Hope this helps

[rider7816]

Try this. Take a large syringe and a short piece of hose and fill the syringe with brake fluid. Loosen the bleed off and attatch the hose and syringe to the brake bleed and fill everything from the caliper up to the master cylinder. The air bubbles want to go up the line anyway and this will push them if any to the resavor . Have had this problem with a dirt bike that I had and it was the only way I could get them to work. Hope this helps

BTW,  thanks for the advice and this too didnt work.   I got so frustrated with it I tore the caliper apart again and wasnt putting it back together until I figured out the problem.

End result, the original piston was the problem.  It looked fine and I didnt "feel" any problems after using emory cloth on it, but, I replaced it with a new piston and problem was solved.

Thanks for all the help

Frank