I decided to refinish the steering damper rod which showed every bit of its 40 years of service. I’ve not tried to restore plastic parts before and I wanted to see how closely I could bring it back to its original condition.
Sanding Out the Scratches
I started with 220 grit wet sanding paper to remove the nicks and gouges. I use water with a drop or two of dish detergent to float the sanding fines off the surface and to help keep the paper from clogging. Then I moved down to 600 grit. Here is the result after 600 grit.
I proceeded to finer papers, 1500, 2000 and finally 2500 grit and I arrived at this result.
It shows a slight shine and there are some scratches visible, but all the large nicks and dings are now gone and surface feels smooth to the touch.
Polishing the Plastic
I purchased Griot’s set of polishes and I have a 3 inch random orbital sander and a palm sander. I and used the palm sander with the 3 inch foam polishing pads. Here’s Griot’s #1 polish with the foam pad mounted on the palm sander,
and the damper after working in the polish and removing most of the residue with a clean shop towel.
And now, on to Polish #2
and the result.
Then, Polish #3
and the result. The finish is approaching a “like new” shine.
And this is Polish #4 for light swirl marks,
and the final product. Almost a mirror finish which closely matches the shine on the stem of the damper rod. I’m pretty pleased with this first attempt at refinishing plastic parts.
I lost some of the detail in the center. I should have masked that off before I started, but I mistakenly thought I could control the sanding to avoid that area. Lesson learned.
Adding a Modern BMW Emblem to Damper Knob
So, I’m going to update the center of the damper knob and add a BMW medallion from a 2004 R1150-RS which I think will be very distinctive touch.
I need to drill a shallow hole with a flat bottom in the center of the damper knob. I got a 3/4 inch Forstner drill bit at Home Depot.
This style bit is designed for drilling a flat bottom hole. The emblem is very close to 7/8 inch, but I couldn’t find a 7/8 inch bit, only a 3/4 and 1 inch. I opted for the 3/4 and figured I could taper the top of the hole by hand to insert the emblem.
I drew two pencil lines at 90 degrees across the center of the knob. It took a couple tries to get the center located. Then I clamped the damper in my vice with rubber jaws. I used my battery powered variable speed drill and drilled at a slow speed to prevent melting the plastic material.
The emblem is about 3 mm thick so I was careful to make the hole just a bit deeper. Since I have to taper the top edge with a knife, I don’t want the hole too deep.
I used a utility knife with a new blade and slowly carved an angled edge to the hole test fitting the emblem until it set at the right depth. The back of the emblem has a glued material used to stick it to the plastic bracket on the 1150-RS. I trimmed away the protective paper so I could insert the emblem.
As you can see the knife slipped a couple times. 🙁 SO, back to sanding and polishing the knob to remove those. I used 220 grit wet sanding to get the scratch out, then moved to 320, 400, 500, 1500 and finished up with 2000 grit.
To polish, I used the Griot 3 inch polisher and started with #1 polish (coarse) and finished up with #4 (extra fine).
I installed the emblem using black silicone seal. I peeled the protective paper off the back and put enough silicone seal in the hole to have the back of the emblem touching it with just a bit squeezing out the side. I cleaned the excess silicone off with a clean blue shop towel. Last, I used a little Armor All on the knob.
After about 2 hours of work, here is the final product installed on the bike with the polished upper fork brace. I think the emblem adds a nice touch to the R75/5.