Honda CB750 Sandcast
The Restoration Shop => Parts Q&A's and Feedback. => Topic started by: vnz00 on May 12, 2018, 04:57:25 am
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Hi all,
I’ve just stripped down a nice set of original carbs. These have the 28 caps, but aren’t the earlier, long choke arm version. The float bowls have this casting mark inside all 4 bowls (the set all appears to be in nice original shape). I’m wondering if anyone can shed some light as to whether these are earlier or later features? Thanks.
Regards, Steven.
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Steve, hopefully someone will report in! the carb setup that came with my 232 chassis, is the long arm, horizontal vent type. i would need to remove a bowl to see if there are markings like you have posted. Hopefully someone will know and report their findings to your answer!
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Engine 1682 , carbs happen to be apart. Long choke arm (66mm) 90° vents and interiors of bowls are smooth with no marks visible.
Lester
Now that magnification was mentioned I reinspected during daylight.... (3) with a backwards 2 and (1) with a backwards 1 no logo marks
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I pulled three sets of early (not straight vented brass tube) carburetors from my parts, I found that two sets of bowls have a 2 cast in inside bottom and one set has a 1 cast in bottom. Both numbers appear backwards in the casting. I have many more sets I could dig through, but I would suggest these numbers are from the dies, to identify from which die each bowl was produced. I must point out that these numbers are very small and not easy to see without magnification. All 12 bowls were marked.
I ran a foundry for many years and this is typical for cast tooling, but there could be other reasons for the marks.
It would be interesting to hear from others, as I would guess there might be more than three distinctions identified inside the bowls.
Best,
DW
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Went out to the shop and dug through some more early carburetor sets, all five of theses additional sets are all early Sandcast style carbs with single raised dimple feature on top of body.
Looks like we can say there are four different types of features cast into the bowls, since these are all 28mm carb sets. See atached photo.
Same as Steven's photo but with a 1 cast on opposite side of body.
Interesting observation, the other style bowl with 1 and 2 numbers (without the other feature) are cast backwards in the bowls.
Best,
DW
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Thanks for the info DW.
I checked a set of bowls from #18xx, original to the bike. These had the backward cast ‘1’, other spare bowls I also checked had a combination of the backwards 1 & 2’s, also from 69 carb sets with the single raised hump. But none of the more complex castings like the ones in my picture.
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Update - I found a single horizontal brass vent carb I have which had the same strange casting as the first pic I posted, with a number 2 cast into it. this may be an early feature. Ill have my hands on a complete set of horizontal vent carbs in the new couple of months and will post pics of the bowls they have.