Topic: 1975 CB400f rear brake spring install

[Jp from Oz]

Hi everyone, I am currently working back on the bike 1975 CB400F I started 5 years ago(haven't touched it in over 2 years due to personal issues) and I can't seem to get the rear brake pedal spring in right. Can anyone post some pictures of how the large brake pedal spring sits between the shaft and frame? I've seen some but not from the angles I need most. I have tried searching here and on the web and found nothing that really helps. I am sure it's not that hard to fit properly but I am making it look that much harder.
cheers in advance
JP.

Sent from my SM-G930F using Tapatalk

[jakec]

from the forum here. I t may be impossible to install the shaft with the swingarm installed. Not sure.



http://forums.sohc4.net/index.php?topic=51957.175

[Nurse Julie]

I have a piece of rubber tube over the end of the spring to protect the frame where the end of the spring hooks round. Not sure why the spring isn't hooked around the frame in the other posters photo 🤔 I can't see how that would work.

[Alaxy Galaxy]

Julie's pictures is more accurate as to what it should look like: the brake rod attachment point should point upwards.

It's impossible to get the spring on the brake pedal pivot shaft without removing the shaft, and chances are you need to remove the brake stopper arm and the swing arm to do so.

[jakec]

the first photo ( not mine) it's installed correctly there is just not tenstion on the spring so it's not contacting the frame yet.

[Nurse Julie]

the first photo ( not mine) it's installed correctly there is just not tenstion on the spring so it's not contacting the frame yet.

So the photo you posted isn't answering the original question anyway. It is not showing the spring or brake rod attachment in the final fitted position.

[jakec]

Can anyone post some pictures of how the large brake pedal spring sits between the shaft and frame?

ok boomer

[Jp from Oz]

Ok so it seems I have it the right way according to these photos you guys have put up, but i have no tension... so I must have done something wrong inside rear drum when I installed the new brake pads years ago. I will have to investigate it further and take it apart to see.

Sent from my SM-G930F using Tapatalk

[jaytee-nz]

There are two springs that fit at each end of the two brake shoes linking the shoes together. These provide the spring tension for the brake arm that connects to the splined shaft which in turn acts as a cam inside the drum to push the shoes apart and make contact with the drum itself.

[Jp from Oz]

So I checked i had installed my drum brakes correctly. I am pretty sure they are right. Now I thought I'd check the inside diameter of the brake drum to nake sure it was serviceable, didn't look good.
The manual says 160.0-160.3 with a service limit of 161mm.
I measured mine at 161.32
Is there a way to fix this without replacing the whole hub?

Sent from my SM-G930F using Tapatalk

[jakec]

I strongly doubt that that’s your problem. The front hub on my 350 (interior) is out of round and it causes my braking to be kinda weird, but not a big deal. People on here have 125,000 mile bikes and their hubs are fine.

When you install the actuator arm on the outside of the hub, it has a non-splined section that tells you which way to put the arm. There is also 1 “free” spline on either side. Basically you can choose to advance or retard the actuator arm about 5* either way. You probably advanced it unknowingly, and thus can’t  build tension even with the adjustment screw all the way down (12mm special nut on the brake arm).

[Jp from Oz]

I strongly doubt that that’s your problem. The front hub on my 350 (interior) is out of round and it causes my braking to be kinda weird, but not a big deal. People on here have 125,000 mile bikes and their hubs are fine.

When you install the actuator arm on the outside of the hub, it has a non-splined section that tells you which way to put the arm. There is also 1 “free” spline on either side. Basically you can choose to advance or retard the actuator arm about 5* either way. You probably advanced it unknowingly, and thus can’t  build tension even with the adjustment screw all the way down (12mm special nut on the brake arm).

Thanks Jakec, I changed the position of the actuator arm just slightly like you said and now I can get some tension on the brakes. But, is the brake spring supposed to be taught on the frame because mine is still loose until i put pressure on the pedal. It just seems odd if that is supposed to be normal.

Sent from my SM-G930F using Tapatalk

[jakec]

If you look at the pic I posted and the one posted after me, the part where the brake arm attaches should be at 12 oclock, vs. 9 oclock like in your photo. Hard to tell what's wrong now without a side shot showing everything in the brake linkage.