Topic: New paint on tank is FUBAR!

[sparty]

Well, if I didn't have bad luck, I wouldn't have any luck at all.  I just got back from a ride and parked the bike.  I did a quick walk around and saw that there was stuff splattered all over the right side of my gas tank.  Turns out that it was brake fluid!  So, now I have two problems.  1. My MC is leaking at the lever junction.  2. My new paint job (two weeks old) is toast on the right side of my tank.

What would cause the MC to leak - seal gone bad?  If I am going to have to rebuild the bastard, I'll put on my super bike Nissin MC and run all new braided hoses.  Until then, the bike will have to remain parked.

Just when you think you have everything finished… these tricky CBs really test your patience.

Sparty

[Bob Wessner]

What would cause the MC to leak - seal gone bad?

Could be. As I recall, the only thing between the fluid and the outside world on the lever end, is the seal that mounts on the piston. If it gets by that, all that's left is pretty much just a dust seal.

[nickjtc]

It's these trials and tribulations that make us love the beasts all the more. Kind of like the relationship we have with our sig. others.

[ProTeal55]

Sorry to hear man  
Better than turning around and seeing your bike fall over I guess.. ?
Just put the newer master on the thing and forget about it..

[cmorgan47]

had the same thing happen last week, though i think that my master cylinder issue is because i mounted it on cafebars and it's at a mean angle.  thinking of replacing it with a modern relocatable one.

and my "custom paint" is spray can primer, so fixing that is easy.

[StevieMac]

I'm really sorry to hear that sparty.

Make sure you check it's not leaking where the banjo bolt connects to the MC.  Mine was and it was leaking down underneath the assembly and showing up around the lever joint.  I thought I needed to rebuild the MC but all it needed was a new (less rusty) banjo bolt and a new washer.

[sparty]

Does anyone know what size banjo bolts are on the stock set-up for a 1972 CB750?  Are they 10mm x 1.25 pitch?

Sparty

[sparty]

I'm really sorry to hear that sparty.

Make sure you check it's not leaking where the banjo bolt connects to the MC.  Mine was and it was leaking down underneath the assembly and showing up around the lever joint.  I thought I needed to rebuild the MC but all it needed was a new (less rusty) banjo bolt and a new washer.

Yeah, I checked that already.  It is clearly leaking at the lever.  Thanks man.

Sparty

[StevieMac]

Does anyone know what size banjo bolts are on the stock set-up for a 1972 CB750?  Are they 10mm x 1.25 pitch?

Sparty

I think all the years are that size.  My '78 750 and '72 500 both use that size.

[sparty]

Does anyone know what size banjo bolts are on the stock set-up for a 1972 CB750?  Are they 10mm x 1.25 pitch?

Sparty

I think all the years are that size.  My '78 750 and '72 500 both use that size.

THANKS!

[Hop on a Honda]

Thanks for the post.
I am in the middle of giving the beloved CB750 K5 a birthday with a liquid overhaul on ever thing that needs painting.
I also have replaced all the Hydraulics on the front  brake, including all lines and fittings.
But I did replace all the banjo washers. They are a once only use. Replace then as as sure as the sun comes up they will leak if yiou don't.
There is also a Goo that can be used on the threaded parts?. "Recommended"
I heard that the banjo fittings should be torqued down too. What PSI you say, I have no idea.
Sorry about the paint, that fluid is the worst nighmare a man can have when it stuffs paint.
Dave Australia.