There are sessions on this restoration where you make real progress. Then there are sessions where the more you dig in, the worse things look. This was one of those. The CB750F seat pan went from “I can patch this with JB Weld” to “I might need to find a whole new one” in the span of about an hour, and I am still processing that a little.
There was other progress too. The trunk got cleaned and treated, the seat spring clips finally came out after soaking in PB Blaster, and the gas tank trip to Jeff is actually getting scheduled this week. So it was not all bad news. But that seat pan is sitting in the back of my mind right now.
Table of Contents
Trunk Cleanup Done
Before getting into the seat, a quick update on the trunk from the CB750F trunk removal last session. I gave it a good clean with some foaming all-purpose car cleaner and hit the metal bands on the backside with a wire wheel to knock off the worst of the corrosion. Those bands are riveted on and I have no way of drilling them out and replacing the rivets, so I masked off the interior plastic and hit the metal with rust reformer instead. Not a perfect solution but probably good enough for something that lives under the seat.
The foam ear plug trick for plugging threaded holes before painting is working out well. I buy them by the box for riding anyway, so they are always on hand and they pop right back out with a pick when the paint is dry.
Getting the Seat Spring Clips Out
The spring steel clips that hold the seat cover in place have been soaking in PB Blaster since the last session. Some of them came out in usable shape. Others had so much rust that the PB Blaster essentially dissolved what was left of the structural integrity and they just fell apart when I touched them. I need to track down replacement clips at some point because I do not have a full set anymore.
Getting the intact ones off was still a fight. I used the mini picks to work between the vinyl cover and each clip, rocking them out carefully. None of them came off easily and I broke at least one more in the process. These clips are old, brittle, and not forgiving when you push them.
The Spinning Stud Problem
Once the clips were out I tried to get the trim hardware off so the seat cover could come free. This is where the session got frustrating. There are studs that hold the trim piece in place, and at least one of them had corroded to the point where the threaded section just spun freely in its channel rather than allowing the nut to thread off. I tried vice grips, different socket sizes, PB Blaster, and at one point seriously considered reaching for the oscillating tool to just cut the thing. The problem with cutting it is that it is a specialty fastener with a large button head, and I have no idea whether I can find a replacement.
I got most of the fasteners out eventually. That one spinning stud is still soaking. A few days with PB Blaster and maybe it will break free. If not, I am going to have to make a decision about whether cutting it is worth the risk.
What the Aftermarket Cover Revealed
Here is the thing I did not expect. The whole time I have been looking at this seat, I assumed the brown vinyl cover was original because I could not find a brown replacement cover online anywhere. Everything available is black. Turns out there is a reason for that. The original Honda seat cover is black. At some point in this bike’s life someone recovered it in brown vinyl over the original, which means the stock black cover is underneath. Or what is left of it anyway. Once I got partially into the cover removal it was clear the original had gotten torn up enough that someone had put the brown aftermarket cover right on top of it.
The foam pad underneath looks rough but not disastrous, which is the one bit of good news from this section of the restoration.
The CB750F Seat Pan Situation
This is the part I was not prepared for. I knew the seat pan had rust going into this. I had looked at it in earlier sessions and figured the JB Weld steel stick epoxy I picked up would be enough to bridge the worst spots and fill in any gaps. That plan is out the window now.
As I got the cover further off and could actually see the full extent of the damage, chunks of metal started coming away. Not surface rust. Actual structural metal just disintegrating. The areas I thought were patchable are not. The seat pan on this bike is likely beyond what any epoxy repair can address, and I am now looking at finding a replacement.
The complication is that the CB750F seat is supposed to be different from the K model seat. The F has a trunk section that sits underneath where the K does not, which means the two are not directly interchangeable the way some other parts on this bike are. I joined a CB750 enthusiast forum and a Facebook group specifically to see if anyone has a lead on a replacement F seat pan. That search is just getting started.
If I do find a seat pan, the cover is the easy part. They are available through the vintage CB750 parts suppliers and I have had that option in the back pocket for a while. It is the pan itself that has to come first.
The Gas Tank Is Finally Heading to Jeff
Some genuinely good news to end on. I spoke with Jeff and we are getting together this week so I can drop off the gas tank for the patch and weld repair. I am also bringing the rear brake calipers so he can use heat to free the seized pistons that have been fighting me since back when I tackled the rear brake caliper removal. Both of those problems have been sitting open for a long time and it will feel really good to have them off my plate.
There is no timeline on how long Jeff will need with either piece. I will drop them off and let him work around his own schedule. But getting them out of my garage and into capable hands is progress regardless of when they come back.
Ride With Me
If you want to see how the seat pan search plays out and whether the gas tank comes back in one piece, subscribe to the WaltInPA YouTube channel
so you catch every session as it goes up. If you know someone who has dealt with a rusted out seat pan on a vintage Honda and found a solution, send this one their way and have them leave a comment. And if you want to be part of the conversation as this build keeps moving, come hang out in the CB750F Restoration community in the WaltInPA Discord where good people talk through exactly this kind of thing.
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