Author Topic: CB750 (k5) Pedal Metal?  (Read 624 times)

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evoskuil

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CB750 (k5) Pedal Metal?
« on: April 28, 2020, 11:55:40 PM »
I've had this bike for 36 years and always believed the brake, shift and kickstart pedals to be chrome plated steel. I believe these parts to be stock original. After grinding off part of one I found the chrome-colored metal to be solid, including welds. Put a magnet on them and it sticks, so doesn't appear to be stainless. But it sure looks and feels like stainless no matter how deep I go. I've tried all three, same. Am I losing my mind?

Offline 70CB750

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Re: CB750 (k5) Pedal Metal?
« Reply #1 on: April 29, 2020, 03:44:10 AM »
Austenitic stainless steel is non magnetic.   I believe it is because of the added nickel.  Ferritic SS is magnetic.

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Offline pjlogue

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Re: CB750 (k5) Pedal Metal?
« Reply #2 on: April 29, 2020, 05:50:32 AM »
If it is OEM stock I guarantee it is chrome plated steel. 

Honda made these bikes with production cost in mind.  They wanted to offer a dependable bike at the lowest cost they possible could.  To do so they used the lowest cost production methods they could.  High end alloy on parts that didn't need it were out of the question.  Also remember this was mid 1970's and the technology wasn't like we have today.

-P.

Offline DaveBarbier

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Re: CB750 (k5) Pedal Metal?
« Reply #3 on: April 29, 2020, 08:04:12 AM »
Definitely chromed steel. Grinding any steel it will look bright and shiny. Look under the brake pedal foot pad, I bet it’s rusted.

Offline ekpent

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Re: CB750 (k5) Pedal Metal?
« Reply #4 on: April 29, 2020, 08:40:02 AM »
Definitely chromed steel. Grinding any steel it will look bright and shiny. Look under the brake pedal foot pad, I bet it’s rusted.
  They usually get a little rust in the serrations also on the pad where your foot works the brake pedal.

evoskuil

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Re: CB750 (k5) Pedal Metal?
« Reply #5 on: April 29, 2020, 03:34:52 PM »
Thanks for the replies. I’m familiar with each of these perspectives, which is why I find it so interesting. I’ve cleaned up chromed steel before, and this is nothing like that. I’ll have some more pics in a day or two. My first day looking at this is documented here: https://hondacb750k5.wordpress.com/2020/04/26/foot-parts-prep/

After the post above I did some more widespread sanding. I then found that this applies to all of the supposedly chrome plated pedal parts: shift, brake, kickstart (including knuckle and pin). They can all be ground, filed, sanded apparently indefinitely and polish up to the exact same look. I even deepened the grooves in the foot grip to restore its bite after years of wear.

The chrome content of the metal appears to be uniform. It rusts where in regular contact with iron, and where it collects (often very salty) road water, such as under the pedal. It’s magnetically attracted, which is certainly possible, though I didn’t expect it. None of these suggest it isn’t stainless. I just find it hard to believe Honda would have done this. If they did then properly polishing up the surface restores the metal to its original corrosion resistance (getting the surface chrome density back above 12%).

evoskuil

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Re: CB750 (k5) Pedal Metal?
« Reply #6 on: April 29, 2020, 05:07:35 PM »
I just added this text to my blog post on the topic (pics in the link):

“By letting the part sit overnight exposed to the elements we would expect to see a color change between chrome and freshly exposed steel. Sure enough, that’s what we see. So it is indeed plated. But the color change seems the opposite of expected. The more deeply ground, filed and/or sanded areas are more silvery, while the other areas, which would be the plating, look reddish.“

https://hondacb750k5.wordpress.com/2020/04/26/foot-parts-prep/