Howdy all,

These forums have been great for my newer bikes so I thought I'd give y'all a holler for my first Harley, my 1976 FLH. I live in a rural area and the only shop around here that works on Harleys is the dealership over in Danville, and they ain't exactly gung ho on servicing Shovelheads. Old Rocket Roger passed away a few years ago and he was the only one I knew of in the area that new these older bikes.

The issue I have is the front brake lever will fall to the bar if I grab it SLOWLY. If I yank on it hard the brake will grab and hold and the lever holds steady until I ease off pressure. If I do slowly ease up on it and pull it again it will fall towards the handlebar. I have bled the system and the problem crept back in. Up until recently the system has worked flawlessly.

I'll give y'all as much information as I can about the components of the brake system. The lines are braided stainless steel and the caliper is GMA. Here is a pic of the caliper:



Here is a pic of the front master cylinder:



I THINK it may be a Drag Specialties unit like this:
Drag Specialties Master Cylinder Assembly 3/4 in. Bore Dual Disc - DS-290708
but I cannot say for sure, it has been on the bike many years.

There is no brake fluid leaking anywhere in the system that I can find. I replaced the master cylinder gasket when I last bled the brakes a couple of months ago. The system has always had DOT 5 brake fluid in it to my knowledge.

Given the strange behavior of holding when I grab the lever quickly does anyone have any ideas as to what to try next? I'm not against replacing the master cylinder if necessary but I thought I should put this scenario out there for folks more knowledgeable than myself to consider.

Thanks in advance for any and all ideas.

 

I dunno, man.....sounds like a bad MC or a leak...or, it needs to be bled more...

 

If you can squeeze the lever slowly to the bar you have a bad master cylinder

 

the master piston cup is by-passing fluid. when you apply quickly, the quick build in pressure expands the cup and it seals to the bore but when applied gently, it does not flare out tightly and leaks around the lip.
hopefully, the bore will be "OK" and a repair kit is all that is needed.

https://i.ebayimg.com/images/g/r8oAA...YbO/s-l300.jpg

 

Thanks for the info Kingglide. Drag Specialties makes a rebuild kit for that master cylinder so I think I'll try that first. Hopefully it's just some worn out internals.

 

Think of it as hemorrhaging on the inside like said by the post above.
No big deal, a fresh set of cups and a light scuff you will be all fixed up

 

Thanks for the info y'all. The Drag Specialties rebuild kit did the trick. That dang snap ring was a nightmare though. Hole was too small to get my pliers into but I finally talked it into seating.

 

"I finally talked it into seating" ... Amazing what 4 letter words can accomplish :>)