Honda CB750 Sandcast

Restoration of Sandcast #97

markb · 814 · 327872

markb

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Thanks for the tips guys. 
Brother....... !  Looks like that engine was sitting in a lake. 
The owner claims it was a barn find.  I just think it was behind the barn!
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?)


Joe K

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Mark,

It seems that maybe the oil was drained out of it.  Otherwise, the parts inside the transmission cover wouldn't be rusty.  I am curious to see what the gears look like after you split the case.  I hope they are in good usable condition.  I am sure you will do fine on the restoration.  You have experience and it's a labor of love.  I have my sandcast restoration just about complete.  Everything is done, except for assembly.  My bike will be both blue/green and red.  I have a freshly painted blue/green set done and will be getting the red set painted very soon so that I can change the color of the bike each season.  That way, I don't have to buy two sandcasts.  Remember, any heartache you go through, do to the rust, etc. issues will be long forgotten when you have your early VIN restored.  You are a very lucky guy to have such a low VIN.  I feel fortunate to own a sandcast too.  4646.

Joe K.
« Last Edit: November 14, 2010, 12:02:11 pm by Joe K »


markb

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Warning: some of the following photos are graphic and are not for everyone.

It took a while but I got the rotor cover off.  Didn’t want to break this one.  Not pretty inside.  Had to cut the head of the screw off to do.  It still doesn’t want to come out.  More soaking and more heat and try later.


The clutch cover actually came off quite easy.  More horrors though.


Flipped her over and got the pan off not too much trouble.


Here’s the top half.  The cases split too without much trouble although the countershaft bearing holder was a PITA.


And the bottom half.


Close up on the gears…


…and the other half.


They look bad but actually I don’t think there as bad as they look.  After wiping off some the “gunk” on the surface there’s shiny teeth underneath.  I need to get everything apart and inspect everything more closely but I hope and can save most of 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?)


markb

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Thanks for the tips guys. 
Brother....... !  Looks like that engine was sitting in a lake. 
The owner claims it was a barn find.  I just think it was behind the barn!
In the pond!
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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Mark,

It seems that maybe the oil was drained out of it.  Otherwise, the parts inside the transmission cover wouldn't be rusty.  I am curious to see what the gears look like after you split the case.  I hope they are in good usable condition.  I am sure you will do fine on the restoration.  You have experience and it's a labor of love.  I have my sandcast restoration just about complete.  Everything is done, except for assembly.  My bike will be both blue/green and red.  I have a freshly painted blue/green set done and will be getting the red set painted very soon so that I can change the color of the bike each season.  That way, I don't have to buy two sandcasts.  Remember, any heartache you go through, do to the rust, etc. issues will be long forgotten when you have your early VIN restored.  You are a very lucky guy to have such a low VIN.  I feel fortunate to own a sandcast too.  4646.

Joe K.
There was about a quart and a half of oil but also water.  I think the bulk of it might have leaked out the drain plug.  It wasn't the correct one, which reminds me, I have to check out the threads in the oil pan.  I have to keep telling myself all day how lucky I am. :D
Mark
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?)


cb7504

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Mark:                           
       Believe it or not most of the rust and gunk will be removed with a good cleaning. The motor no doubt had allot of moisture/water in it at one time. The finished product will be well worth your time and effort, especially with your bike having very early vins. Marty K.       


kp

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Mark,
Yippee-Ky-O
The amazing thing is the lack of any damage to the cases or the front sprocket area. That's a BIG plus for E100 There are some items that will be critical to retain such as the crank but I personally would try and keep as much of the transmission as possible just to keep authenticity of the engine. We are so fortunate to be given this pictorial tear down and commentary
I come home each day and go straight to this thread just to see what new adventure has been taken or to be treated to another morsel of new information.  :o
I'll bet the rusty-tin from over the pond is also watching with ..................................... antic............................................................ipation  ;D
Yabba Dabba KP


markb

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I forgot to mention there was some good news.  The nuts on the con rods came right off and I pulled the crank out.  Number 2 & 3 pistons slid right out by hand without much force (they were at the bottom) and they look great.  The seller did say that it had been rebuilt before it was parked (abandoned) and it doesn’t look like it had been run much after the pistons were put in.  The rings were loose and no carbon on them.  Both 1 & 4 are loose but didn’t want to come out yet.  I wasn’t going to force it.  I’ll soak them for a couple more days.  Still working on getting the jugs off too.  If the cylinder ends up looking OK I’m considering using it and the oversize pistons.
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?)


Steve Swan

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Marty's right.  Alot of what is seen is likely rusty scum over a film of oil on the actual parts.  Areas that have less exposure to an oil film such as clutch could have more rust, but would be good to bead blast the metal clean to see what rust damage actually exists.  The other more concerning areas would be where the parts were in water for sustained time or where the water/oil levels met. 

The most important areas where we can hope there's no damage are load bearing areas, i.e., cam lobe faces, bearing journals and/or any other surface that bears or distributes a load.


markb

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I went to take another stab at getting the cylinders off.  Maybe it’s my imagination but it seems that the top machined surface of the cylinders is closer to the top fins than I remember.  I’m not sure how well this photo shows it but the machined surface is barely higher than the fins.  Is it possible this surface has been machined?  Anyone have a cylinder that they can accurately get a dimension from the top machined surface to the bottom surface where it sets on the case?  Or better yet, the depth of the two counterbored holes on the rear, center studs?  They seem shallow to me too.
Thanks,
Mark

« Last Edit: November 15, 2010, 07:29:26 pm by mark1b »
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?)


Wayne

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Mark
I don't have the measurements but I'll throw my 2 cents in for what it's worth. First, measuring against another casting may not get you your answer. Castings, especially sand castings are not twins of one and other. When the parts are machined for final assembly the "deck height" is established at that time. In wedge style combustion heads that sets the "quench" or "squish" area for the heat transfer between piston and head. In a "hemi" engine like the SOHC there is no such thing as the flat "quench" area so the whole piston head serves as a heat transfer agent to the hemi combustion chamber.

Being that you have OS pistons I'm wondering if someone didn't shave the deck to up the compression a bit more?? It's an old trick we used to use when racing stock motors and an easy one on overhead cam engines as it didn't screw up the valvetrain geometry. If you got torn down it was unlikely you would be caught.

Having said all that I'm not sure if the service manual covers deck height/piston to valve clearance or not. Even if it is shaved, and your clearances/tolerances are OK you should be able to run it. Compression will be a bit higher than stock. You might be able to offset it a bit if you can find a thicker head gasket. Lots of times aftermarket gaskets tend to be thicker than OEM.

Now if someone has a measurement for the man I'l lbe quiet.  ;)
[size=


1941wld

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Hi Mark,
In looking at your insides, the best product I've used on rust is saferustremover.com. It will not harm chrome or paint. It will remove rust from parts rusted together. It's $100 bucks for 5 gals. I just soak my parts for till the rust is gone.  Parts previously seized together just fall apart. I would put the whole motor in the solution and watch the magic. Your suck bolt will be free. It's amazing.

Conrad



magpie

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Mark,
I can't measure it because the engine is together but this is a picture of the cylinders of engine 260. It does seem to have more of an edge or lip than yours. This probably confusing things more.
Cliff.


ashimotok0

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Don't know if this is any use but on my Diecast K0  (Oct 69 1010382) the depth of the counterbore is 0.93mm on rear two centre stud holes and the height of the machined surface above the fins varies between 0.8 and 1 mm

Brilliant posts by the way Mark. I 'tune' in each day to see your progress!  


Best regards

Ash
« Last Edit: November 16, 2010, 05:57:51 am by ashimotok0 »


markb

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Thanks for the great feedback guys.

I've used that Safe Rust Remover before, thanks for the reminder.

I'll measure those counterbores tonight. 
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?)