Honda CB750 Sandcast

Restoration of Sandcast #97

markb · 814 · 284087

markb

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Although not really a sandcast thing, I decided to use “28” carb parts for a restoration more accurate to leaving the factory.  They were replaced in a recall as described in Honda Service Bulletin #15.

As (most of) you all know, this feature is identified with the number 28 embossed on the carb tops as shown on the left.  Also note that the cable adjuster is much smaller (as well as the rubber cap) for a 5mm diameter cable instead of the 6mm diameter replacement.


The tops are thinner and had a gasket.  Maybe someone can chime in on this but I don’t think the gaskets are used on later carbs.  At least I’ve had some sets that didn’t have them.


The caps are also thinner…


…and the slides are shorter.  The “28” slides are 41mm long and the later slides are 46mm long.


And the springs are shorter.  I had a couple of sets of “28” carbs but was missing a couple of springs.  I had some made up to exactly match the originals.  Here are specs.
Material: stainless steel spring wire
Wire diameter, .9mm (.035”)
Free length, 128mm
Outside diameter, 18.5mm
Active coils, 15 ˝
Total coils, 13 ˝
Closed ends
Load @ 55mm = 1.15 lb.


I had the carbs rebuilt by hondaman from the SOHC4 site and bought some excellent reproduction 5mm throttle cables from vnz00 (thanks Steven).  At least for now when I twist the throttle and let go it snaps right back.  I think they will be just fine.
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


Garry32

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Hi Mark, Can you give me more info on vnz00, I am looking for a few 5mm cables.Do you have any springs spare.You can p/m if you want.
Garry :)
« Last Edit: December 01, 2015, 12:51:09 pm by Garry32 »


markb

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PM sent.
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


Erling

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What about the diameter of 46m carburettor slides?
They seem to be 2/100 mm smaller.
In the day only changed the slides.
Stronger springs were too much for my weak handcuffs.
Never had a sticking slide after that though.
An explanation to what exactly caused a sticking slide I've not heard.
Only happened when warming up engine too enthusiastic on twist grip!
Maybe some heat distortion on carb body before proper and even warm?
           Erling.


markb

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When I put the slides in the carbs they seemed the same to me but 0.02mm isn't very much.  When I get a chance I will measure them and report back.
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


ken736cc

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I am in need of a 5mm cable also. Can you give me more info on vnz00. Thanks
I've seen the future, I can't afford it.


markb

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He is an active member here.  If you look under members you can find him and send a PM or email.
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


markb

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I have some pictures of #97 on display at the Petersen Museum. Sam (ujeni) sent me a link for a blog he saw about the re-opening and the motorcycle display. Here it is if you want to check it out.
http://www.bike-urious.com/the-petersen-museum-is-back/

These first three pictures are from the blog.


They are in chronological order from newest in the back to oldest in the front.


Everyone knows the red sandcasts are fastest and displayed going downhill makes it look even faster.  ;)  :D


The rest of the pictures are from the guy who originally called me and doesn’t work there anymore but happened to be there for the re-opening.


She’s in pretty nice company.  There is a lot of red around.  A blue/green one would have looked nice too.


Here you can see a Triumph Bonneville to the right and there is a Vincent Black Shadow that you can’t see ahead of the Triumph, a couple of my favorite non-Japanese bikes.


I think that’s a couple of Harleys in front and there is a Kawasaki and Ducati behind.


Here are a couple of close-ups.


I like this shot.


I’m really looking forward to going to see it.
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


kenhan

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Wonderful!
Congratulations!

/Ken
1969 CB750 Sandcast #5084 - running
1969 CB750 Sandcast #5128 - Running
1970 CB750 next project
1975 K2 (K3-5 don´t exist in Sweden) - Running
1981 Goldwing 1100 Interstate


4pots1969

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Mark... very sincerely... You have the right to brag on this magnificent result!!

Gerard  ;)
« Last Edit: December 14, 2015, 12:31:55 pm by 4pots1969 »



markb

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Thanks for all the nice comments guys.
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


Sgt.Pinback

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….offset 8 on the chain adjuster.stopper.  :D



Sorry and maybe late... but may I ask.... that chain adjuster stopper has to be zink plated?
Cheers, Uli (Leonberg, Germany)


4pots1969

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A big Yes for the ZP... but do not put washer for the bolt "8"... ;)
« Last Edit: December 14, 2015, 12:33:09 pm by 4pots1969 »


markb

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That's correct. The washer was removed quite a while ago.
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)