After getting the rear fork removed, the next job was obvious. CB750F rear fork cleaning was the agenda for the night, and for most of the session it went about as well as I could have hoped. Then I made a mistake with a can of carb cleaner that turned a simple touch up job into a full repaint. Let’s get into it.
Table of Contents
Knocking Off the Big Stuff First
Before reaching for any water or chemicals, I scraped the rear fork down with an old plastic business card to knock off the bulk of the grime without gouging the paint underneath. Forty years of flung chain oil came off in satisfying chunks, and underneath it the paint looked better than I expected. There is rust here and there, which tracks given the age, but nothing that looked like it was going to be a fight right out of the gate.
The grease fitting end had a genuinely impressive amount of buildup, almost fibrous in texture from decades of grease mixing with road grime. I was relieved to find the dust covers on the ends are actually hard plastic rather than rubber, since that meant they came off easily without any risk of tearing a seal I would then need to replace.
The Cleaning Process
From there it was the usual progression. A blast of Dawn dish detergent and Awesome Orange degreaser to get things wet and moving, followed by a plastic brush for the bulk of it, a Scotch-Brite pad for anything stubborn, and a brass brush reserved for the truly tough spots. None of this is exciting to watch, and I will be the first to admit that a video of someone scrubbing grease off a metal tube is not exactly thrilling content. But it is the actual work, and the actual work is what gets this bike back on the road.
Once I had knocked down the bulk grime enough to handle the fork without getting covered in grease every time I touched it, I went back through with a wire wheel chucked into a drill to hit the rusted spots specifically. This is where I got a genuine surprise. Anywhere the paint had rust bubbling underneath it, the wire wheel popped it off with almost no effort. You could practically peel it with a thumbnail. But anywhere the paint was still solidly bonded, that same wire wheel did essentially nothing. I was fully expecting to end up with bare metal everywhere I touched with the wheel, and instead the factory paint held up far better than I gave it credit for.
Where the Carb Cleaner Mistake Happened
This is the part of the session that turned a simple night into a much bigger project.
Brake cleaner worked great on the areas where I had flaking paint and exposed rust. It cut through the old oil and grime without issue and left those spots ready for primer. The problem came when I used what I thought was the same product, but was actually carb cleaner, on areas where the paint was still solid and I just needed to clean off some leftover grime.
Carb cleaner and this particular paint do not get along. At all. What was supposed to be a quick wipe down turned into paint softening and reacting in ways I was not expecting. I had genuinely thought brake cleaner and carb cleaner were close enough to interchangeable, mentally lumping them in with the lacquer thinner and solvents I used to work with years ago in a wood shop finishing room. That assumption cost me a clean, simple finish on this part.
The fix is to scuff the entire rear fork with a Scotch-Brite pad and prime the whole thing rather than just touching up a few spots. What I thought was going to be a quick spot-paint job is now a full repaint. Lesson learned the hard way, which seems to be a recurring theme on this build.
Masking and Priming
Before priming, I masked off the original sticker on the rear fork. It is not critical to the function of the part in any way, but it has been on this bike since the 1970s and I want to keep it if I can. I also masked around the grease fitting areas and any through holes where fasteners will eventually run, since I do not want primer building up anywhere that could affect reassembly tolerances.
Without a way to hang the rear fork for full coverage, I primed one side, let it dry overnight, and planned to flip it and hit the other side the next day. The full satin black topcoat is still waiting on me actually finding the right paint. I have been meaning to get to AutoZone or Advance Auto for over a week now since neither Walmart nor Harbor Freight carry satin black, only gloss or matte. That errand keeps getting pushed to tomorrow.
What’s Next on the CB750F
Once the rear fork is fully primed, scuffed where needed, and finally painted satin black, that piece goes back into the pile of parts waiting for reassembly. The end caps still need some additional cleanup once the painting is sorted out.
Beyond the rear fork, the punch list from the last update still holds. The trunk, tool tray, and battery box are next off the bike, followed by the wiring harness and ignition coils. The rear brake caliper piston is still seized and parked until it can travel to Jeff alongside the gas tank for proper heat treatment.
Ride With Me
If you want to see how the rear fork repaint turns out after this carb cleaner detour, subscribe to the WaltInPA YouTube channel
so you catch the next session. If you know someone working on an old bike who might make the same brake cleaner versus carb cleaner mistake I did, save them the trouble and send this one their way. And if you want to swap notes on old Honda paint or anything else on this build, come hang out in the WaltInPA Discord where good people talk shop and occasionally save each other from boneheaded mistakes before they happen.
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