1974 Master Cylinder Cap Stuck... Help!

[bparsons]

I feel like I'm losing my mind... I can't get my master cylinder cap to unscrew. The master cylinder is off of the bike and off of the handlebars.

I believe this is the original front master cylinder and has the round cap (versus the rectangular kind with the screws (4)). Is this reverse threaded (I have tried clockwise and counter clockwise)?

I've hit it with some WD40 and nothing. Hope I'm just being an idiot and missing something! Thoughts?

Will post a pic.

 

[5twins]

No, it's not a reverse thread, but it may have been on there since 1974, lol. WD40 probably won't help much, try some real penetrating oil like PB Blaster. It may take a day or two of soaking, maybe some heat from a heat gun too.

 

[bparsons]

5twins - thanks for the tip. Will let it soak. Here is a pic of the unit, think this is original to the bike?

 

[5twins]

Yes, that looks like an original. You might want to pull the piston out and inspect the bore. That unit looks pretty rough. Maybe it's toast inside, in which case it wouldn't much matter if you got the cap off, lol.