CB750F Rear Master Cylinder

[tractorguy50]

Hello All!

I recently picked up an '82 CB750F with 12k miles! It is a little rough, but I am tackling one issue at a time. First on the docket is no rear brakes. When I took the master cylinder off, the underside of the boot was filled with rust. I managed to get the snap ring and the washer out, but it looks like the piston, cup, and spring are a permanent part of the housing. What I can see of the bore is pitted out.

Does anyone know of a source or a modern-ish equivalent that would bolt up in its place? I have seen something about newer bikes that have master cylinders that might work, but nothing definitive.

I appreciate any help!

Cheers

 

[Raggaren]

I think This should work.
But you have to use a different
hydraulic Brake line
That connects to back of cylinder vs side
https://ebay.io/m/d0jFeB

Picture of hose as example of hose ends

 

[VFFreedom]

If your looking for parts Ebay and vintagecb750.com have parts. Vintage has a code on here to get a percentage off. Dennis Kirk is a reputable site as well.

 

[Raggaren]

If you’re looking for parts Ebay and vintagecb750.com have parts. Vintage has a code on here to get a percentage off. Dennis Kirk is a reputable site as well.

OP is looking for whole assembly..
Problem is they only have rebuild kits.
Vintage cb does have a universal fit rear M cylinder similar to the fleabay link I posted..
And if you are lucky enough to find a decent used one.
Most likely it will need full rebuild????

 

[tractorguy50]

Yes, looking for a complete assembly. Has anyone had any luck with the vintage750 master cylinder?

 

[tractorguy50]

Good news everyone! I managed to get it apart without destroying anything. I am still in shock. The PO gave me a rebuild kit for it, that is this weekends task, along with the calipers. The pistons are stuck in the rear and the right front brake. Maybe PB blaster will save the day again.

 

[Raggaren]

Nice.
On my other 78 750f
Both front and rear was frozen as well..
Sprayed some pb blaster and keept pumping/applying brake to push piston out of caliper

 

[SenseAmidMadness]

If you have access to compressed air, it can also be a good helper when disassembling brake components. Shoving air in the hole where the banjo bolt goes can often push a piston out the other side. I've used it to pop pistons out of calipers too when disassembling. Just gotta be careful not to let things fly across the garage...

 

[tractorguy50]

It looks like the seal around the piston has swelled and is jamming the piston. I can press it in with a c-clamp, so I know it moves, it just does not want to move out. I will try some air.

 

[mrtwowheel]

I used the grease gun way once, worked really well and messy. Can't remember how I hooked it up.

 

[tractorguy50]

I got them out by using the front master cylinder. I need new hoses anyways. I pulled all the calipers off and popped the pistons out. If one needed to rebuilt, they probably all do (and they do). The brake hose going from the splitter to the right front caliper must have collapsed. Nothing got through no matter how hard squeezed.

Now for some steel wool and elbow grease to get everything cleaned up.