Last Friday I picked up a clean 73 RD350 that had been sitting for years. It needs all the usually stuff done to it from sitting for so long so I started today messing with the front brake master cylinder and ordered a rebuild kit for it.
Here's my question - is that teeny tiny hole the one that usually gets clogged in the master cylinder supposed to go all the way through?
I cannot remember if that hole is supposed to be open or not - I've tried using .020 safety wire and it will not go all the way through so I thought I'd ask.
If it is supposed to go all the way through then does anyone know the drill size so I can ream this hole out?
Thanks!
It goes through to the piston cylinder. I use a high "E" electric guitar string (.009", I think) in a pin vise to work my way through them, then flush thoroughly with brake cleaner.
Acetylene torch tip cleaning set of little wire pokers works good too.
Can someone else please confirm that this hole circled in red goes all the way thru
I shined a bright light in the opening and I can't see any evidence of that hole going all the way thru even when looking from the underside - also I find it hard to believe that it would be that stubborn to clean out.
Anyways I'd like to know for certain before I put this all back together again because the circlip and rubber boot can be a pain
Thanks
That is the return hole. If you apply a brake and the return hole is clogged your brakes stay applied.
All the way through? I do believe it goes through to the piston side.
it does go thru to the main bore. do -not- make it bigger.
take master apart before clearing it out.
A BIG thanks to all that replied - I ended up drilling it out with an undersized drill bit - I would of never thought that it could get so clogged up where safety wire and a guitar string did absolutely nothing but bend.
Thanks again :thumbs:
Quote from: forexer on January 18, 2021, 05:06:04 PM
A BIG thanks to all that replied - I ended up drilling it out with an undersized drill bit - I would of never thought that it could get so clogged up where safety wire and a guitar string did absolutely nothing but bend.
Thanks again :thumbs:
On another note, if you have guitar string or steel braided wire and a drill that will chuck it up. It will act as a drill bit. That's how I de-Caswelled my tank crossover tubes. Yeah, I couldn't figure out how shoving playdough inside the tubes would prevent the top of the hole from being clogged with it.