Before and after: The Laverda SF2 fork yokes were pretty rough, but after media blasting they’re ready for fresh paint.
We’ve wanted a good media blast cabinet for, oh, like forever, so actually having one makes us almost giggle every time we find an excuse to put it to work. We picked up our TP Tools Skat Cat 40 blast cabinet about a year ago, and since then it’s become a central piece of equipment in the Motorcycle Classics garage, an alchemist's dream that lets you magically turn lead into gold by transforming time-worn parts into like new forms, ready for refinishing. Just recently, we blasted our way through a trio of steering bits; two motorcycle related and one bicycle.
The painted bicycle stem.
The bicycle stem after blasting.
The bicycle stem after polishing.
First up was the upper fork yoke on my daughter’s 1980 Moto Guzzi V50. The original plan was to replace the Guzzi’s pitted fork tubes and leaking fork seals. The upper yoke had to come off to pull the tubes, and it seemed pointless to put it back on with its scruffy and worn black paint. Guzzi seems to have gone back and forth on yoke finish at the time, sometimes painting them black and others leaving them in a natural aluminum finish. On the V50, the bottom yoke was a natural aluminum finish and the top was black, so I opted to take the top yoke back to a natural finish.
Previously, I would have used a chemical stripper to remove the original paint. That works OK, but it’s slow and tedious compared to having a blast cabinet, and there’s a fair bit of clean up and final prep to get to a finished result. Using the TP Tools blast cabinet, it took maybe five minutes tops to completely strip the yoke. Once stripped, I worked it over with a buffing wheel, starting with Brown Tripoli compound before moving to White Rouge. That took longer than stripping the yoke, and maybe even a little longer than had I opted to repaint it, but the result is a clean, natural aluminum finish, and it looks excellent back on the bike.
Next up was refinishing the ugly off-white handlebar stem on my road bike. The stem was a freebie from a friend, but I wanted a natural finish and was actually on the cusp of getting a new one when I did the Guzzi. I went through the same process as with the Guzzi’s steering yoke, and like the Guzzi, it only took a few minutes to strip. And being a smaller piece, it was a pretty quick job to polish it up. I didn’t go for a mirror finish, but could have if I’d wanted to put in a little more effort.
That was hardly done when I turned my attention to replacing the steering head bearings on a 1974 Laverda SF2 750. Pulling the yokes off, the paint on the upper yoke was much worse than on the Guzzi, and the lower was no better. Unlike Moto Guzzi, Laverda was consistent with the final finish on the yokes, painting all of them something between a flat to satin black. The paint on the Laverda yokes was thicker than on the Guzzi, so it took a little longer to strip them, taking maybe 10 minutes each to get them how I wanted them. I took both pieces to get powder coated, but haven’t collected them yet. I’ll post picks of the finished yokes shortly.
The Moto Guzzi V50 fork yoke before blasting.
The Moto Guzzi V50 fork yoke midway through blasting.
The Moto Guzzi V50 fork yoke blasted and polished.
A quick note on blast media:
We started with TP Tools’ suggested blast media, Skat Magic Abrasive crushed glass. That gave excellent results on aluminum, which is what we’re mostly working with, leaving a perfect base finish ready for primer and paint. When it was time to restock media, we turned to our local Tractor Supply Co. store, where we picked up a 50-pound plastic drum of their house brand U.S. Minerals crushed glass media. Both are rated as medium grit, and both work well, although we think the TP product performs better and lasts longer, and with less dust, which is a downside to crushed glass versus glass beads. The upside? Crushed glass cuts faster. The price was nominally the same, the Skat Magic priced at $31/50 pounds and the TSC glass media priced at $33.99/50 pounds. We’d go back to the Skat Magic if we could, but shipping costs pretty much kill that option for us. Next time around, we’ll stock up with glass beads to see how that media performs relative to the crushed glass. And finally, we’ll also order another air filter for our Skat Blast HEPA Vacuum ($27.95 for a standard filter, $42.95 for HEPA). We’re on our second so far, and we’ll be curious to see if we get longer filter life with glass beads, as the filter seems to load up quicker than we’d expect given our blast cabinet’s relatively light work load. — Richard Backus