Topic: '74 cb750 Brake Question

[SadGruffman]

Hey guys,

First time poster here. I have a '74 CB750 that I'm trying to get running. Wiring harness was stripped off by me about 8 years ago during a rebuild I never finished. Moved twice since then, lost some parts, bought some parts...

Planning to replace all the controls and levers, I have a new (brake lever with a master cylinder) and I'm curious, will -any- master cylinder brake lever work with the older brake system? Or does it require a certain master cylinder to make pressure etc and engage the brake?

Can provide photos if necessary, figured I'd post what I'm workin' with

[scottly]

Hi Sad, welcome! What is the diameter of the piston on your MC? The stock MC has a 14mm piston, and anything larger will give a stiff feel to the lever. Some guys will fit a smaller MC to increase the hydraulic "leverage".

[SadGruffman]

Hi Sad, welcome! What is the diameter of the piston on your MC? The stock MC has a 14mm piston, and anything larger will give a stiff feel to the lever. Some guys will fit a smaller MC to increase the hydraulic "leverage".

Do you mean the rubber internal piston itself and not the whole housing? It's a rectangle, its 3" long, 1 1/2" wide, 1/4" thick.

[scottly]

The internal piston diameter: look for any markings on the outside like a circle with a line through it and a number like 14, or a fraction like 1/2 or 5/8.

[SadGruffman]

No numbers on it, there is a circle with a line through it at the center of the piston. Measured the diameter of the circle, it's 5/8"

I checked the old ebay order, it was from years ago, says "Motorcycle Clutch Brake Levers Master Cylinder Kit Reservoir Set OEM Universal"

[scottly]

5/8" is too big for a single 38mm caliper. Does the stock one work? If it does, it would be a better fit.

[SadGruffman]

its been sitting but i'm sure its fine. I'll flush the line with fluid this week and see whats up.

Currently getting a piece of titanium to mount all the electronics to the stock battery box, hoping it fits under the side cover... That's kinda project part 1. Part 2 will be brakes.

Is there a sweet spot for the master cylinder that you all recommend? If not, I'll pop around the forums and read up on what others have done.

[scottly]

Titanium? What electronics are you mounting on the stock battery box?

[SadGruffman]

I have some 12" x 12" titanium 1/8" thick. Going to cut it down to fit an M-unit, Starter solenoid, and new regulator.

Attaching it to the old battery box.

upload is template #1, we've gotten much smaller since.