Hello,

I have inherited a 1972 FLH and am getting the bugs out of it. It sat for about 3 years. When it was parked everything worked in good order. I rebuilt carb and it is up and running now I need to get it stopping.

I can pump up the front brake and the brake is there but as soon as I let it go the lever drops off all the way to the throttle.

I first bled the **** out of it. No air same issue

then mityvac't it same issue

so took caliper apart/ rebuilt had some debris new o-ring and dust seal bled -same issue.

I don't see any leaks at the master but I am at a loss any help would be appreciated.

-Six

 

Not holding pressure....

1. Make sure the brake line where it connects to the master cylinder and to the brake caliper is correctly fitted and tight.

2. Make sure the bleeder valve it completely closed.

3. Remove master cylinder, take it apart and install new master cylinder repair kit.

4. Are you using DOT 5 or DOT 3; do you know what was originally in there?

 

fittings are all good, bleeder is closed, if not there would be a leak that I could see. I see no leaks.

I am using Dot 5, supposedly that is what was in there.

Master cylinder rebuild kit is next I guess but shouldn't there be other symptoms to justify that?

still confused but thanks for suggestions Panz!

-any other suggestions out there?

would a bad reservoir cap gasket be an issue? or if it was originally Dot 3 or 4?

 

I would clean and rebuild the master cylinder and also clean out the brake line (spray it with brake cleaner then hang up to dry). Put it all back together start from there. Rebuild kits aren't very expensive.


Carl

 

The original gaskets in the cap are terrible. They don't last so if you buy a replacement, buy several. Also I don't know what type of bars you have. Does the mc sit level in the riding position? In 72 dot 3 was used but they changed the requirement to dot 5 which is much better.

 

over haul the master and like was said // pay attention to the location of the master it wants to be level --

Note - i have taken the master off the bar and hung it by the hand lever tapping it with a punch lightly than let it hang over night and have had some luck in getting it to complete purg all the air - ( the tapping brings the air up into the master from the lines and caliper )

 

Cap gasket is just some thin material with a filter screen to keep $hit out. So if you tighten it it should basically seal.

The master cylinder is made up of a plunder, spring, coule of washers, felt gasket and some rubber seals. Any of that rubber fails and your gonna get a leak down because pressure will not build up and hold when you apply the brake lever.

So given that you have the other things I queried you about checked off the list, I would look at the master cylinder unit. Does it need a rebuild? As has been mentioned rebuild kits are cheap and plentiful. The only other thing I would check would be the bore of the master cylinder unit once you have it apart.

If it is seriously pitted, then a rebuild kit will get you naught because air will leak around all the grodydiness that has built up on the inside of the bore...meaning new unit is in order. But I would still do the rebuild thing first provided the bore looks clean.


I am using Dot 5, supposedly that is what was in there. K...if it were my bike and I wasn't sure, I would pull trhe entire assembly apart, clean it all and lubricate the parts with DOT 5 and then put it back together just to make sure!

 

I ordered the rebuild kit,

the master is on a set of 18" apes. so in parked position the fluid should be in a good spot not to let air in , I would think. I will let you all know after I rebuild the Master Cylinder

Thanks for all the replies.

and yes it is all definitely dot 5 now! lol

-Six

 

rebuilt master, lever is all good now! Brakes still seem a little soft in my opinion but I am told that's how a shovel head is. I will probably change the line just so everything is 100%. Thanks guys here is a pic

 

Glad you got the brakes in order.

Nice looking bike you have there. That puppy has to be LOUD running those shotgun pipes though!