45 rear Brake

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I have a 43 WLA engine in a 46 frame (it has the 3 bolt clutch cable). I have no idea what year the backing plate is for the rear brake. Recently the brake sometimes grabs hard at slow speeds when I slowly engage the rear brake. The bike pulsates like the brake grabs and lets go but I don’t feel any pulsating in the pedal. This doesn’t occur at higher speeds. The shoes are reproduction shoes with lots of lining left on them from when I put them in. I also replaced the rear brake drum with a reproduction one and it still does it, occasionally (same with the original brake drum)

I know the actuating camshaft had some play in it and it’s time to pull the rear brake and take a look at it. I also learned two different actuating camshafts were used on the 45 rear brakes. How do I know I have the correct one for the brake shoes I am using?

If there is any play in the actuating cam, especially excessive play, is there a way to put a bushing in? I don’t see a bushing in any parts books and I wonder if there is a specific size bushing to use, material, etc., that is available for the 45s.

Thanks
Ron Papasso
AMCA 3129

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For those that have been reading this post I have an update. I pulled the rear brake assembly off this weekend and found a few things I was not expecting. Two problems showed themselves right away regarding the reproduction brake shoes.

1) The shoe castings are different than a pair of NOS shoes I found. There is an angle at the cam side of the shoe that is cut in to prevent the shoe from hitting the raised area in the brake drum. The reproduction shoes are worn in this area and so is the raised area in the brake drum. When compared to the NOS shoes the angle is not cut correctly on the reproduction shoes. This causes the shoes to drag on the raised area inside the brake drum.

2) The hole in the shoes near the cam where the top spring attaches is close to the cam and on the NOS shoes the hole is further away from the cam. Having the hole closer to the cam does not tension the spring much at all, I can insert and remove the spring with just my fingers. On the NOS shoes the hole is further down and I cannot install the spring with my fingers, it is about ¾” short to span from one hole to another. On the NOS shoes the spring has to be installed into the shoe holes first and then with lots of force applied to spread the shoes they can be installed onto the cam.

Problem #2 seems at this point to be the biggest problem without having much spring tension pulling the shoes together. With minimal spring tension the problem may be that the leading shoe contacts the brake drum and catches causing the leading shoe to self energize.

I ordered another set of brake shoes to see if the casting has been updated. If not I can grind the proper angle in the reproduction shoes and weld up the existing hole location for the top spring and drill a new hole using the NOS shoes as a pattern. If that fails I will clean up the NOS shoes and get them “de-rusted” and relined.