The front brakes on my 80 ironhead are not working at all. I replaced the fluid and bleed them real good and it seemed to help for about 1 ride.

it is dual disk with HD calipers, aftermarket braided lines and an after market master cyclinder.

I replaced the fluid and blead the rear and it works great now.

After i blead the fronts it would hold pressure and then slowly let off. It got worse very quickly. Now you can walk up and pull the lever all the way down with no or little resistance. If you pump them up they will build a little pressure and then die down to nothing very quickly.

I cant throw money at this bike but i need advise on where to start. The simplest and cheapest first. then maybe a trial and error until i get it right.

here is a pic of the master cylinder if anyone can help me identify it.





soory for the crappy pic
i can take more if needed

 

Sounds like the master cylinder seals are shot. Rebuild or replace.

 

That's pretty much what I thought.
I assume that I need a specific rebuild kit for that master cylinder, but I don't know who makes it.

 

Try Googling the make, model, year and front master cylinder. Look at Google images. You might get lucky and visually match it up that way.

 

this is the exact same as mine. stock i guess

http://www.jpcycles.com/product/2400772

and this i think is the rebuild kit i think i need, but not totally sure

http://www.jpcycles.com/product/2400390

 

I have that same brake system on my 1978, and had it on my 1980. This is what i have done and mine works very well.

Remove and dismantle the complete brake system. Separate the brake lines. Remove the fittings from the master cylinder and calipers. Use only correct size sockets [not open end wrenches] for all this.

Spray brake parts cleaner thru all of the brake lines and fittings, especially that 3-way fitting under the fork stem. I cleaned the whole d@mned system but overlooked that part. When i went back in to clean it, it was full of crud. Could never bleed them properly.

Dismantle the calipers. Simple job, not many parts. Clean thoroughly. There are two rubber seals. Do not get brake parts cleaner or any solvent on the seals - just brake fluid. I never had to replace them, just cleaned, lubed with brake fluid and re-used.

I used compressed air to pop the pistons out, catch them in a thick towel. They pop out easily - unless they are badly cocked in there. Before you pop them out look carefully at the way the two rubber seals install - take a pic or two, so you get them back in correctly. Bath everything thoroughly in brake fluid for re-install. Really make sure the pistons go in straight. Lube them and the seals with lost of brake fluid.

Master cylinder may need a kit, easily available thru an indie bike shop or on-line seller. It is tedious to dismantle - you need a good quality 90` snap ring pliers - not one of those cheapie ones with the interchangeable parts. You have to put it in a vice, use whatever tool to stabilize a part under spring pressure, then remove the snap ring. Similar install. This from memory, details foggy.

FSM has good, helpful info for this.

 

cheaping out on brakes will get youa ride in a ambulance

 

I get that, just not sure what direction to go on rebuilding the master cylinder. I think that is the kit I need but if there is a better one I'm all ears

 

That is the correct rebuild kit. 45063-72 is the part number from the Factory Parts Catalog for the correct rebuild kit. I have used that one myself, tho from my indie not from J&P.

 

Ok cool I might go ahead and order it.

When I blead the back brake I got extra fluid and pulled a lot of fluid throught the system with a small vacuum pump. Until it looked real clear . It works great now.
Hopefully the rebuild kit for the front and bleeding it real good will work