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Bleeder screw size (1980 CB750 Super Sport)

ROHK

CB750 New member
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Guys do you know the size of the front and rear bleeder screws?
Thread in mm
length in mm

Both front and rear bleeders on my 750 are completely frozen, bike was stored for 15+ years
Tried every trick to remove them without success (heating, brute force, etc)
I will probably need to drill and rethread and replace with some aftermarket kit.

Any suggestions?
 
you could try cleaning out the rust from the hole and put penetrating oil down leave it a day then heat them up. if the dust caps weren't on they soon corrode where the seat is .mine were seized and i kept doing that for a few days and eventually got them out
 
Done that, rust remover, WD40, heating, been on it for several days.
The head of the bleeder is toast so i will have to replace them anyway

1. Will first try a bolt remover, if it works no problem, OEM bleeders
2. If not, will drill it out, rethread and find something that fits.

It is a PITA when people leave bikes in a garage/barn for so long, this bike was probably stored AT LEAST for 15 years.
 
i understand mate mine was stood outside for 12 years { one fork full of water } and i had snapped a few self welded bolts and studs. i think they call it galvanic reaction? the rear brake master cylinder was toast the fixing bolt snapped and once the rest was out i was looking at crumbling powder that you could scrape out leaving no thread..
 
I'm not sure if you can get them where you're at, but here in the US it's possible to buy "brake bleeder repair kits". They include a set of one brass fitting and a bleeder screw that goes into that fitting, and you drill and tap a hole with NPT threads for the brass fitting to go into the caliper.

The most common bleeder screw thread size is M8 by 1.25mm. I know that's not the right size for my own 1980 CB750K because those screws didn't fit in my front caliper, and I have no idea if that's what your bike uses.

If you can find the parts, you may be able to use some Brembo bleeder fittings from Ducati/BMW rear brake calipers that have a large M14 thread (probably 1.50mm pitch but I'm not sure) and use an M10 x 1.0 bleed screw with a 10mm hex for tightening. Those would be a relatively easy installation as the bleed fitting itself with the large thread uses a copper crush washer to seal the brake fluid in, and they're straight threads and not tapered like the bleeder repair kits I mentioned above.
 
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