Survivor Chop: Rear Suspension Repair

I've had this bike out on the road for a while now, and after some tuning, it's been great.  While doing a normal eyeball inspection, I noticed that the lower bushing on the left side axle plate was coming out.  Trailing plunger suspensions typically use an upper and lower bushing in the axle plate to slide along the suspension shaft.  These are most often either pressed in or held in by a circlip.  

Typical aftermarket trailing plunger configuration.

Notice at the bottom of the spring, the bushing is visible. It should be up in the axle plate.

To disassemble the suspension, begin by lifting the rear of the bike off the ground, removing rear tire, and disconnecting anything that is connected to the axle plates, such as a chain guard. Next, clean the lower nut underneath of the assembly and inspect for a grub screw or other retaining device.  If any retaining device is present, remove it from the nut.  Loosen the nut a little and you'll notice that the chrome cup at the top should begin to lift up off of the frame's spring housing.  

Next, use a C-clamp or a valve spring compressor to keep the assembly compressed and remove the lower nut.  Use a rag on the contact surfaces of the clamp or compressor to prevent damaging the paint or the chrome. Once the nut is removed, slowly and carefully loosen the clamp to relieve pressure on the spring assembly.  The spring assembly will expand about an inch or so before reaching it's free length.

Valve spring compressor positioned so the lower nut can be removed.

Yank all the pieces out while noting how they were installed.  I disassembled both sides to inspect and grease.  The lower bushing on the left side axle plate had almost completely fallen out.  It should have been pressed in as there is no groove for a circlip.

Lower bushing as it was removed from the bike.

The lower axle plate bushing was only in about 0.125 in.

The original bushings were Bunting P77-8 (specs TBD).  The inner bore was very clean and showed little signs of wear.  It seems as though the outer diameter just didn't fit snug with the inner diameter of the axle plate's bore.  Since the bushing is in good shape, I decided to use a punch and place a series of indentions around the outer surface.  Before doing this, the bushing was somewhat snug in the axle plate, but not much of a press fit.  After adding the indentions, the bushing pressed in with a reasonable amount of force.  

New indentions added with a punch to increase the interference for the press fit.

With the repair made to the bushing, I inspected the rest of the suspension parts.  The shafts on both sides showed scoring, but it had already been filed down smooth.  The scoring did not correspond to any marks on the existing bushings and there were fine file marks on both shafts. This leads me to believe that somewhere along the 50 year timeline of this bike's existence, someone else had already rebuilt the rear suspension.

The last step before reinstalling is to clean, polish, and lubricate everything.  This was the only part of the bike I was unable to fully clean and polish when I first began cleaning it up, so I wasn't going to slack in this area.  I degreased all the bits, then used steel wool (0000) with light oil on the more heavily corroded parts and Blue Magic Metal Polish Cream for the last round on everything.  Once everything shined as much as it could, I lubricated the sliding parts with some fitting grease and checked for any issues with travel.  

Inspected, repaired, cleaned, polished, and lubricated.

To reassemble, stack the short spring, then the axle plate, then the tall spring into the frame spring housing.  Slide the suspension shaft through the middle of the stack and compress with your C-clamp or valve spring compressor.  Reinstall the lower nut and retaining hardware (mine had a grub screw to which I added a dab of thread locker).  Add grease to the assembly through the zerk fitting.  Put the rest of the bike back together and check for proper function under the bike's full weight.

After a test ride, I noticed no difference at all... which is what I hoped for.  If I had waited until the bushing had completely fallen out, I might have noticed some vibration or worse.  Without the lower bushing, the rear wheel might rotate sideways slightly, causing the chain to jump the sprocket which could result in the addition of a lovely bay window in my engine cases.