Front MC leaking again, this is twice in 5 years. Is it the DOT5 eating the seal?
94 FXSTC

 

I don't believe so... Is not the Dot 5 a silicon based fluid... It's supposed to protect the seals... You have something else going on there.... Maybe dirt scored the plunger shaft and is slowly wearing the seal.... You live near a coast line... Salt?

 

Try changing the mc cover. Maybe you've got a bit of a warp in it. I got tired of chasing leaks on my Shovelhead and swapped out the stocker for a Nissin off a GSXR.

 

It's definitely at the plunger, it doesn't squirt out (I said squirt), but more just seeps out. (Like it has a VD). Just started when I just changed out my levers. Has to be a coincidence, unless I somehow knocked the seal loose.

 

Sounds like a complete rebuild with new plunger kit.... Time.... Sometimes just a seal will do it but sometimes it's in the shaft of the plunger... Don't forget as well, the guide for the plunger could be worn allowing the plunger to move around a little...

 

without looking, i assume the master is of the chevron cup type??
last change was after-market???
if so, there are a lot in you boat. i too have this issue on my 74ch. i think the issue is with the cup. the bore is clean and spec'd out so that leave the cup lip. if you think about it, all the pressure and wear is just a fraction of an inch on the cup. i do not think the cup to be too hard although it very well could be as it wouldn't take much to mess it up. the thing about glycol based fluid is it does have a tendency to soften and swell the cup where silicone does not so that too may be an issue. one thing for sure is parts ain't parts any more.
just installed a new kit in mine a few months back. on old stuff, even the hd dealer near where i live just forks over after-market crap.

 

Ya, I don’t think the controls are stock 94. The kit they sold me doesn’t match.

 

Seems to be a Drag Specialties master cylinder with a 5/8" bore. And it would seem I dislodged the plunger cap when I replaced my levers.