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Discussion Starter · #1 ·
I'm rebuilding the master cylinder on my '78 Honda 550.

Do both the holes in the reservoir serve a purpose for this bike?

I can't tell if it's simply a blind hole or if it's a completely clogged passage that I need to clean.

I can't get compressed air to go through nor a small awl.

Thanks.
 

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Both holes are necessary. One is supply, tiny one is return that lets fluid back into master cylinder, allowing pucks to retract.

The only thing I could ever find to clear out the plugged tiny hole is a sewing needle from the wife's sewing kit.

Good luck with it.

Kirk
 

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Discussion Starter · #3 ·
Thanks kirkn! After much work I was finally able to get my smallest carb cleaning file through the small hole and finish up.

The master cylinder is now assembled with all new parts and ready to go back on the 550.
 

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just as a curiosity, anyone know of a chemical that dissovles/flushes the corroaion and caked brake fluid out of the master, lines, caliper? i kinda cringe at the idea of poking at the holes with bent 'n sharpened paperclips :oops:
 

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+1 on THAT request.

I've never found anything that does the trick, which is why I have to resort to sewing needles and the like.

On the other hand, I've had pretty good luck with that mechanical method... :lol:
 

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well then, is it safe to fill the master cylinder with brake cleaner and then pump it thru the lines and caliper? i wonder what effect it'll have on the rubber brake lines.... danWI
 

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Discussion Starter · #8 ·
I tried carb cleaner in my master cylinder and while it cleaned it up it did not remove any of the caked brake fluid (and there wasn't very much so it was easy to tell).
 

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Sometimes the crust is so bad that no amount of cleaning by hand is going to get the job done.
An ultrasonic cleaner works on master cylinders too.
And then there is always ebay with newer modern master cylinders that just work better.
 

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fasterspider said:
And then there is always ebay with newer modern master cylinders that just work better.

+1 on that, Ray.
I was going to suggest it, but I thought everyone was probably sick of hearing me go on about it.
I don't mess about with brakes, too important.....
 

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tbpmusic said:
fasterspider said:
And then there is always ebay with newer modern master cylinders that just work better.

+1 on that, Ray.
I was going to suggest it, but I thought everyone was probably sick of hearing me go on about it.
I don't mess about with brakes, too important.....
The customer who's bike I am working on now has 5 vintage bikes, 4 of which have hyrdaulic brakes. They all have newer CBR and GL1800 master cylinders on them.
The 5th bike is the one I am working on now with cable pull brakes, it is out of the equation.
 

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Be advised that braking systems have master cylinder piston size requirements....
TOO much "push" volume (dual, multi-piston caliper master) on a smaller, single piston caliper will make the brakes work TOO well.. (touchy, grabby, too quick)...
TRY to use a master with the same piston size (volume delivered) as your "old" master-cylinder.
Stopping/locking-up too easily/quickly is every bit as dangerous as no front brakes...IMHO.
I DO however, also recommend newer masters...Just make sure they are/have the correct piston diameter/volume....
 

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66Sprint said:
TOO much "push" volume (dual, multi-piston caliper master) on a smaller, single piston caliper will make the brakes work TOO well.. (touchy, grabby, too quick).
Oh yeah, there is nothing like that pucker moment from an unwanted stoppie.
 

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Hi Stoppers
If I was happy with the brake leverage of the stock master cylinder I would go for a new master cylinder of the same size. I am not happy with the stock brake leverage of the first generation of Honda disk brakes. So the next time that I deal with the front brake of one of my Hondas I will go with a new master cylinder with a smaller diameter bore and a built in brake light switch.
TomC in Ohio
 

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The one I used on my hybrid 450/400 front end was advertised as for dual disks (I think a 15mm piston, maybe?? - can't remember).
I've had no problems at all, and it does stop in a hurry. And it sure doesn't fade on you.
At the Riding Skills Test, this bike was stopping in less than half the distance that anyone else could, even the crotch rocket types.
Haven't done a "stoppie" yet (thanks Lord), and I only ride in the rain by accident, so.......

That's my experience - and oh yeah, it doesn't leak and screw up my painted stuff !!!
I'm too cheap to re-chrome or buy new parts, so I paint a LOT of small parts on the bike. The first time the old master acted up, it was history.
The new one was a simple bolt-up.



 

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About to order the same one Bill has there since mine does absoultely nothing.
PO apparently lost the reservoir diaphraghm so he ran a bead of caulk under
the cover. :evil: No point in spending over $40 to make the old one work when
I can install a new one for $60.
I was a little leery since the seller says it doesn't matter if I have a single
or dual disk brake but, if it works for Bill, I expect it will work for me.
Hope to let you know in the spring.
 
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