91 Front Master Cylinder - Harley Forum

botzman · #1 05-18-2008, 02:04 PM

Hey guys,

Replaced the front brake line with a Goodridge setup and I can not get the reservoir cover to stop seeping brake fluid. Its driving me nuts. Ive tried it tight, snug, to specs, everything. Could it just need a new rubber diaphragm replacement? It is a 91. No noticeable rips, tears, etc. Thanks. Mike

botzman · #2 05-18-2008, 10:54 PM

I layed the reservoir cover on a flat surface. It seems the edges/corners have kinda lifted upward slightly. In other words, no longer sitting flush. I would think it should be flat all the way around. Gonna have to look at a new one and see. Thanks anyway. Botz

shovelmike · #3 05-19-2008, 10:12 AM

Good morning, Botz. I have been pondering your question....but it seems like you have found the source of the problem. The only bike I have had this issue with is the Shovelhead. The factory handlebars are a buckhorn style (internal non- spring loaded throttle...nice) and the only time the master cylinder is horizontal is when the bike is on the kickstand with the bars turned full lock left. I get a negligible seepage but it is DOT 5 (not harmful to paint etc.) so checking the level a couple of times through the season suffices.
It appears that yours may be more severe that what I deal with, if so I hope a new lid solves it.

botzman · #4 05-19-2008, 10:18 AM

Hey Mike,

I have the exact setup you do. Buckhorns. Never had a leak problem til now. Then I was thinking maybe the new brake line was creating some kinda back pressure or something. Dunno, just exploring all possibilities. I put the old cover in a vice and straightened it a bit. We will see. Might have made it worse for all I know. LOL. Botz

evoKENevo · #5 05-19-2008, 10:55 AM

Hey,Botz
Is the imperfection slight enough to correct by rubbing/planeing the surface of the cover on a sheet of sandpaper layed on the flat surface you checked it on...possibley starting carefully with a flat file ??

frisco-rigid · #6 05-19-2008, 10:14 PM

The brake lines only job is to transfer fluid, they would not "create" a back pressure..

I wonder if the cover is cast or forged with a wee bit of upward angle at the edges..

I actually bent in a upward bow (at the edges) in a cover once cuz after time it developed a downward bow and didn't seal well in the middle.. I don't really remember how I bent it now cuz it's one of those things you just tackle in that devil may care way,, you know,, "this is either gonna work or not", well, it did and I bet I still have it somewhere..

My guess is a worn out rubber seal..

botzman · #7 05-22-2008, 10:41 PM

Hey Frisco,

Being I used a new line made by Goodridge I was thinking that maybe the composite of the line was expanding and contracting due to the sun beating down on it. Seems like a hard coated rubber substance. Must be some steel in there though. Anyway, sometimes I think too much. If you wanna make sure there is no leak use a new rubber (pun intended). Problem solved. Thanks to all. Botz