BSA Motorcycles 1950s

Separating the swing arm (and removing the silent bloc)

The swing arm on an old A10 does not come apart easily. It is held together by the swinging arm fork spindle (42-4362) running through the center of the swing arm. This spindle is held in place by a securing bolt on one end and a nut on the opposite end. I used the following technique successfully for removal of this swing arm:

- remove the bolt on one end of the swing arm and loosen the nut on the other end

- run a piece of continuously 7/16" threaded rod through the holes in the plate on each side of the frame above the spindle, place nuts and washers on the inside of the plates

- torque the nuts outwards to apply a slight pressure on the two plates at each side

- Drive the nut with a hammer until the spindle breaks free

An attempt to drive the spindle out should be made before doing any jacking of the frame to minimize potential impacts to the frame (I have only had to resort to drastic measures like above in one instance). Additionally pry bars and a blow torch may possibly be used for this procedure before attempting to use a jack to force the frame apart (I have never tried the pry bar/torch technique).

Once the swing arm is separated, the inner housings (or silent blocs #42-4662) around the spindle can be removed and replaced if necessary. In my case, I had to remove the silent blocs to prepare my frame for the thermal portion of the powder coating process (to prevent the rubber part of the silent block from catching fire when the powder coating was baked to the frame). There are two silent blocs within the center of the spring arm. These silent blocs are tubular and consist of a rubber spacer sandwiched between a metal inner and outer shell. The rubber spacer and outer shell are half as long as the inner shell (which runs all the way to the center). While the silent blocs could potentially be pressed out (I did not have sufficient equipment to try this approach), I had to use a more destructive removal technique. I was able to successfully remove my silent blocks by torching out the inner rubber. The outer metal shell did not come out as easily after torching the rubber.

If difficulty is encountered with removal of the outer metal shell, a Dremel tool with a 24 inch flexible shaft and a cutter bit can be used to cut one slot along the length of each bushing.

Once the bushing is cut, a long steel rod can be used to knock each bushing out (driving from the opposite side).

Note: I forgot to take this outer shell off my swing arm prior to powder coating (which complicated outer bushing removal and caused scratches to my new powder coating when I tried to get it off).

To put the new silent blocs in, a press can be used or, if you are like me and can't afford a press, than a long piece of continuously thread rod can be run through the center of the bloc and swing arm with washers and nuts at each end to draw the silent bloc into the swing arm. In my case, I found that a 3/4 inch threaded ROD (with nuts) used in combination with two 3/4 inch washers and two 1 inch washers was needed to do the job properly. The inner metal shell of the silent bloc is designed to protrude slightly and is not level with the outer metal shell. To prevent the inner shell from taking any torque, on each side place one inch washer around the inner shell (it fits perfectly), than the 3/4 inch washer, followed by the nut. This method forces all the torque on the outer shell.