Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: exvalvesetdabbler on May 22, 2025, 11:23:35 AM
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My curiosity has got the better of me again.
Is there a difference in the torque arm between the F1 and F2 , noticed this when cleaning one up where it has F2 stamped on one end.
I put some zinc on this as the last job before discarding the zinc plate bath and as I suspected a lot of muck came out of the insides of it.
[attachimg=1]
What are people doing to refinish these? seems too heavily pitted to polish and lacquer. The one currently on the bike got red oxide and engine enamel (just whatever was sitting on the shelf at the time) and it seems to have held up so far?
Regards
Dave
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Just a production mark, loads of them around if you know where to look. The holes in the back and front of the arm block up and the tube rusts from the inside as a result. If you shake one you can normally hear it making a sound like a maraca, unblock the holes with a drill and you can get the majority of it out by shaking and knocking it on something, I filled mine with zinc paint and Waxoyl to stop it doing it again.
That's pretty badly corroded, I'd see if I could find a better one if I was you. I've had them chromed, lasted but needed constant polishing, polished and even had my last one done in ceramic chrome. Some people paint or powder coat them as well.
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I painted mine in satin black to match the swingarm.
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I'd just clean it up/paint it black. Who's going to notice it's not a pristine surface? You can't really see it unless you are down on your knees with a light specifically to look at it! :)
Of course, if you are wanting it to be concours/look like a new bike for sales purposes, that's a different thing.
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It wasn't the finish you'd get that concerned me Mike, it was the corrosion, is it worse inside for instance, is there a chance it can break and cause the brake plate to rotate under braking causing a possible off. I had a good swinging arm that I decided to throw away as the surface finish was similar to that, for the cost of one I'd buy another.
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Good point, of course! I didn't realize there was concern about that actual "structure" of the piece. Yeah - not an item you'd want to fail!!!
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Measure how long it is Mike, from middle of hole to other middle of hole. I'll see if the 500/550 one is the same, broadens the search out if it is. Might even have a spare myself. I buy swinging arm that that them still attached so might have a spare from those.
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The steady arm on my CB400NA Superdream is approx 370 mm long, I have a spare NOS one available if it's suitable.
Not sure how critical the geometry is on the design length.
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Thanks all. I'm not in need of one right now, I was just cleaning up a few bits in my spares box while I had a zinc plate bath on the go and got curious about the numbers stamped on it. The 400N is a different middle part number so probably not the same.
Regards
Dave.
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I'm sure I have one somewhere that's just a flat bar, or with a rib down the middle. Is that a 550 of some sort - no danger of it rusting from the inside, and easy enough to make up a replica.
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Out of interest what is the distance between the bolt hole centers of the one in your spares box?
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I'm sure I have one somewhere that's just a flat bar, or with a rib down the middle. Is that a 550 of some sort - no danger of it rusting from the inside, and easy enough to make up a replica.
550F1 Andy. The 550F2 went back to the tubular shape but was black for some reason, same part fitted to the 550K3.
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Total Length 394 mm
Bolt hole centers 365 mm
In terms of weak points, I would expect the mounting on the swing arm to break first given how thin that is around the bolt holes.
Surprised no one is making them out of stainless.
Regards
Dave
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That's interesting Dave, I've just checked my NOS CB400NA Superdream brake steady arm.
It's in an unopened bag with Honda Part number 43431-413-010 it's Black it measures 395 in length, 365 between bolt centers.
CB400/4 part number is 43431-333-000.
That information makes my NOS brake arm the same as a CB400/4 so probably a much wider market for selling, mine cost me £29.95. I bought it as mine was badly corroded, my replacement swing arm was as new, it came with the steady arm attached.
Last thing to cross check will be the diameter of the holes - that's for another day.
The CB500 K1 has part number 43431-333-000 it would not surprise me if the 43431 part numbers are common as they are all the same length though possibly not all in the same colour.
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Sorry to burst that bubble Ted but the first 5 numbers denote what it is, so every Honda torque arm will begin with the same 5 numbers, as do all seats or petrol tanks for instance. The 3 middle denote the model so the 500 should be 323 not 333.
There will be a difference between the 250 and 400 arms though or it would have matching numbers, bolt hole sizes would be a good bet.
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Thanks for the info about the first set of numbers Ken, I think 💬 the last number I put in for the 500 K1 is a typo so you are correct the middle number is 323.
Either way the torque arm on my 400NA has the same dimensions as a 400/4. Made me wonder if there is a difference in the tube thickness or steel specification.
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Holes are to clear bolt with 10mm shoulder both ends
Diameter of round section of tube 15-16mm, not perfectly round
Regards
Dave
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Looking at the parts diagram it seems like this would be an easy item to fabricate with a piece of steel tubing if there was no available replacement. Cut a piece of tube, flatten the ends appropriately, drill a couple of holes and paint it...Bob's your uncle!!
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If I am correct the CB400/4 & the CB400NA were both in production in common years, does make me wonder why the few common parts such as the brake steady bar do not use the same part number, might be a pre-computerisation era thing.
As Mike says for those with the right tools easy enough to fabricate.