Topic: Rear drum brake "cam" in wrong position?

[Scott S]

 Is it possible to have the cam in the rear drum in the wrong position? I may have re-installed it incorrectly when I disassembled the brakes to polish the hub.

 I'm trying to get the bike back together and it seems I have to hyper-extend the brake pedal to get the rear brakes to engage. They don't "snap" back into position like they should. If I pull on the brake arm (pulling to rear of bike), the brakes will engage and the arm snaps back. Did I put something back in the wrong place on the cam/springs/shoes maybe?

 God, I hope not...I struggled with the master link on a new chain for 1.5 hrs. today. If I have to remove the hub, can I do it without breaking the chain?
 
(Bike is a '71 CB500)

[Johnie]

That cam will pull forward or back if you have the arm off. It is just a rotating cam in the hub. When you activate the brake foot pedal the brake arm should be moving forward. And yes, you can take the rear wheel off without breaking the chain. You may have to remove the chain guard to get the clearance but it can be done. Here are a couple reference pics for you. Click to enlarge...

[Johnie]

Oh, and did you attach the hub brake arm position bracket? That is done before you tighten the axle. It is the middle bar on the pic.

[Scott S]

 Yes, the positioning rod is in place.

 So, there's really no "up" or "down", "left" or "right" on the cam? What am I doing wrong? I can't seem to get the brakes to engage without going through a WIDE sweep with the pedal.
 The arm on the hub only goes on in one position, right? There are two dots that line up and there's a smooth spot on the splines where the bolt that holds the arm on goes.

 I never removed the brake actuator assembly from the frame, so if those  splines are in the wrong spot, they were that way when I got the bike (out of storage for 30 years). Do I need to unhook everything and re-position the actuator assembly in the frame somehow, maybe?

[crazypj]

Usually there is a single spline 'missing' so it is possible to put cam in 180 degrees 'off'
 You can usually adjust operating arm by +/-2 splines, it may not be 'central' compared to 'missing' spline

PJ

[Scott S]

 Crap, that's not what I was wanting to hear. 180 degrees off means I have a 50/50 chance of it being installed correctly. I'm not even sure I removed it! But I think I did when I polished up the hub cover.

 I'll see if moving the arm a couple of splines helps. It's good to know I can remove the wheel w/o breaking the chain.....that master link was a SOB to get installed!

[Scott S]

  Wait a minute....if I had the cam in 180 degrees off then the bare spot on the splines would be off by the same amount, right?
  Meaning it would be on the bottom of the hub instead of the top. That's not what I have. I must be overlooking something here....

[Johnie]

Ah yes, I forgot about that bare spot on the splines to line up the arm. The bare spot should be on the top. Here is a pic of the actuator arm off the pedal. It should be up as in the pic...

[Scott S]

 Ahh....that helps a lot. I don't think I had the arm far enough towards the front of the bike. Also, does the spring go on the inside like that on a CB500?

 Maybe we're narrowing this thing down.....please, please, please...

[Johnie]

Yes, I believe the spring is the same.

[Scott S]

 Success! That last pic was key. I didn't have the pivot arm forward far enough.

 The spring goes on the outside on my bike, though. The splined shaft wouldn't push through far enough with it on the inside. Plus, I referred to some pics of the bike from the day I got it and can see the spring between the frame and pedal.

 Just need to adjust the pedal freeplay and brake switch now.
 Thanks guys!

[Johnie]

Glad you got it sorted out. Now you will be ready to help the next guy with the same situation. Nice job there...

[MCRider]

Success! That last pic was key. I didn't have the pivot arm forward far enough.

 The spring goes on the outside on my bike, though. The splined shaft wouldn't push through far enough with it on the inside. Plus, I referred to some pics of the bike from the day I got it and can see the spring between the frame and pedal.

 Just need to adjust the pedal freeplay and brake switch now.
 Thanks guys!

Don't feel bad, its been amazing to me how many people have had that problem. Usually following a frame teardown or a swingarm removal. Key to remember is the pull part of the pedal pivot goes BETWEEN the swingarm pivot and the frame. So often its rotated backwards and won't work right.