CB750F Rear Caliper Torque Link Cleanup and a Key Win

I am going to be honest with you up front. The seized brake piston from last session is still seized. I threw everything I had at it and got nowhere, so this post is mostly about stepping back from that fight and finding an easier win elsewhere on the bike. The good news is the CB750F rear caliper torque link gave me exactly that, plus there was a genuinely big development on the tank front that has nothing to do with brakes at all.

The Piston Fight Continues, and Loses

Quick recap on where things stood. I had soaked the caliper in PB Blaster, tried working it loose with stacked sockets and an Allen key the way I had seen in a video of someone freeing a similar Ducati caliper, then tried a Torx driver, a ratchet for extra leverage, a 12 inch breaker bar, and finally a 3/8 adapter on my half inch breaker bar. Nothing moved. At one point I even put the whole bagged assembly inside the ultrasonic cleaner on a heat cycle, which mostly just made the bag swell up and reek of PB Blaster rather than free anything.

My dad was texting suggestions the whole time, most of which I had already tried. He sent me the same video I had already watched. At a certain point you realize you and your support network are circling the same handful of ideas.

The lifeline that actually mattered came from Jeff on the WaltInPA Discord. He told me that if I cannot get the piston out before I bring the tank over for the weld repair, just bring the caliper too and we will get it out together, probably with heat. That gave me permission to stop stressing over it. I have lost real time fighting this thing with nothing to show for it, so it is going on the shelf until it can get the proper heat treatment it probably needs.

Pulling the CB750F Rear Caliper Torque Link

Looking for an easier win, I moved to the torque link, the arm that keeps the brake caliper from rotating around the axle when the brakes are applied. Removal was about as simple as this build gets. A castle nut, a cotter pin in an awkward bent position that still came out easier than almost any other cotter pin on this bike so far, and one bolt. That was it.

While I was in the toolbox I picked up some mini picks from Harbor Freight, on sale for fifteen bucks, thinking they might help me get into the rust around the caliper seal. They did not solve the piston problem, but they are a useful addition to the kit regardless.

Treating the Rust on the Torque Link

This part had real rust built up, more than the Scotch-Brite pad or wire brush could handle on their own. I brought out the Dremel with a wire wheel attachment, which made progress but also left some visible scratching, which told me this piece was headed toward a repaint regardless of how careful I was.

From there I worked through sandpaper grits, starting around 220 and stepping down to 120 where the rust was heaviest, then working back up to finer grit to smooth things out. There is still some pitting that is not coming out without removing more material than I am willing to take off, so I am letting that go as part of this bike’s character.

Once I had it cleaned up and wiped down with brake clean to remove any oily residue, I treated it with Rust-Oleum rust reformer instead of a standard self-etching primer. The reformer is designed to convert any remaining rust directly into a paintable surface rather than just sitting on top of it, which should give better long term protection on a part with this much pitting history. I am treating that as both rust treatment and primer in one step, and the satin black topcoat will go on once I track some down. Satin has turned out to be surprisingly hard to find. I have run into gloss, matte, and flat everywhere I have looked, but not the satin black I actually need for the frame components.

The Key Situation Is Finally Resolved

Here is the genuinely exciting part of this update. My dad called to say the replacement key arrived and it works in the ignition. That single piece of news clears a real bottleneck. With a working key I can finally get the gas cap off the tank, which means I can get the tank itself to Jeff for the patch and weld repair that has been sitting on hold since early in this build.

Having the key does not make the tank problem disappear. There is still a hole to patch, a weld to make, and a pressure test to pass before any of this is actually behind me. But it does mean the project can finally move forward instead of waiting on a part that did not exist a few weeks ago. I am genuinely considering hanging around while Jeff does the work rather than just dropping the tank off, partly out of curiosity and partly because I would like to lend a hand if he will let me.

One More Thing I Found

Somewhat unrelated to anything mechanical, I found the original sticker information for this bike’s exhaust system, which states the stock exhaust is a single manufactured unit designed to minimize noise while maintaining performance under normal conditions, and that modifications can negatively affect both tuning and performance. My dad has the original stock exhaust at his place. He had swapped it out for an aftermarket system years ago, but that one has since rusted out, so the plan now is to put the original stock exhaust back on the bike.

What’s Next on the CB750F

The rear fork is coming off next. The seized piston situation is shelved until the caliper makes its trip to Jeff alongside the tank, where heat should finally settle the question one way or another. The torque link just needs its satin black topcoat once I can find the right paint. And now that the key issue is resolved, the tank repair is finally close enough to schedule rather than just talk about.

---

Ride With Me

If you want to see how the tank repair and the seized piston situation both play out, subscribe to the WaltInPA YouTube channel so you do not miss either one. If you know someone fighting their own seized caliper or waiting on a part they thought did not exist anymore, send this one their way. And if you have ideas on freeing a stuck piston that I have not tried yet, or just want to follow along with the CB750F restoration as it moves forward, come hang out in the WaltInPA Discord. Jeff has already come through twice in this post alone, so the track record speaks for itself.