Topic: disc brakes

[Brooklyn Bob]

I've put a '77 CB750K on the road as a covid project.  I've got it running fine but I'm very dissatisfied with the front single caliper brakes.  I've already replaced the whole system, EBC rotor, new aftermarket caliper, EBC HH pads, new brake lines, new aftermarket master cylinder.   Still it takes an inordinate amount of lever effort to stop the bike.  Without the rear brake, which is very powerful, a quick stop would not be possible.  I even changed the master cylinder for a 2004 CBR 600 master in order to increase line pressure, with no significant effect.  The only thing I can think of is the single disc simply doesn't have enough swept area to stop a 500+ pounds bike.  I'm thinking my next step is to convert to double disc.  My first question is, is this a reasonable upgrade?  My right side fork has the mounts for a second caliper.  Did the F or SS models with twin discs use the same single pad calipers as the single disc K model?  It seems the only thing I can't get aftermarket is a front wheel with the hardware and mounts for two rotors.  If that is reasonable path, anyone have such a wheel available?  TIA

Bob

[Don R]

 The 77/78F came with dual discs and they can also be swapped to Honda 30 or 32mm dual piston calipers.
  I converted my 76F to dual discs also using the same front end you have. There are a few posts here covering the job. Ignore any information about using cb550 or 500 speedometer drives, that is an old wife's tale that won't go away.
 
  Another swap is the early goldwing front end with dual discs.
  I'm surprised your setup isn't better than that.

[bryanj]

You are expecting too much from a 40yr old bike, the brakes at the time were classed as fantastic when compared to pre disc bikes

[newday777]

Bob
When you say you put on new brake lines, did you use stainless steel lines or just rubber lines?

[newday777]

Yes you can put a second disc on. Many have done it over the years.

[slikwilli420]

You can certainly add the second disc or just add a better 2 piston caliper. That ebc rotor is a great piece and complimented by a great caliper you can have really good stopping power.

[david 750f]

I don’t believe the CBR 600 master (I think it’s 16mm) will work well with the single 43mm piston that you have. Check out this chart for the proper ratios. You should be able to lock up the front wheel with that setup.
http://www.vintagebrake.com/mastercylinder.htm

[Bankerdanny]

What master cylinder and what kind of brake lines? I put a modern Nissin radial master and braided plus thinned and drilled OEM rotors by Godffery's Garage on my 750F and they have great stopping power. My 550F just had the OEM master, the thinned and drilled rotor and braided lines. It also stopped really well and I challenged it in the Colorado mountains back in 2017.