Honda CB750 Sandcast

Here we go! Restoring 576/748

Wayne · 180 · 70771

Riccardo

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I agree with KP.

I've had experience on my  both sandcast engine, restored until now.

My welder did a great job with TIG.

My welder in those cases add and add pure alloy with TIG, a very alloy statification.

In this way the finns goes to increase themself and after the welder job is very easy remake the same aspect and size with very small tools with drill and flexible cable to do a precision hand work.

Because i retain that you'll sandblast the engine, i can assure you that will be impossible to find the zone of the weld.

The sanblast action will do to the engine a regular silk aspect, obviously depending from the mesh used.

And after repaint you'll have a perfect engine.

Moreover, i retain not easy weld the fin in the deep trought the fins because the terminal part of the TIG has about 1,5 centimeter of diameter.

Riccardo
Your Italian friend.
737/940 Restored
1081/1362 Preserved
1256/665 Restored - ex Owner: Chris R.
10253/10315 (K0) Next project
1969 - Kawasaki H1 Mach III low ign cover - Restored
1969 - Kawasaki H1 Mach III high ign cover - Restored
1971 - Kawasaki H1A - Restored
1973 - Kawasaki H1D - Preserved
1973 - Kawasaki Z1 Blackhead - Restored
1971 - Norton Commando SS - Preserved
1978 - Honda CBX - Unmolested Museum Quality
1988 - Honda CB 400SS - Unmolested
1997 - BMW R80 GS Basic - blue frame - Museum Quality
2007 - BMW HP2 Megamoto - blue frame - New


Wayne

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Encountered a bit of a problem with the side stand on this old girl. Seems it was bent/broken and the tab was not welded back into place correctly.

As you can see, stick weld was used and a huge gap was filled at the rear leaving the tab at the wrong angle:



And from the front side:



After checking on a couple of pics from other members frames I decided to cut my tab off and see what we have. What we found is, the reinforcement plate had torn up from the rear and forward and that's basically about where it was welded back into place!

When we ground away the weld and tapped the old plate back into place we felt we could pretty well tell where the tab should be positioned. A few marks on the frame and the cutter came out again. We tack welded om a new reinforcement plate and tried to position the tab using the measurements we had taken earlier. We know we are on the money in the fore-aft position. The question is have we got it right as it rolls around the frame? I think we're close but it's difficult without another bike to compare to. Any input is appreciated. I'm also just going to tack weld it and put the wheels beck on to see how it sits. Mu biggest concern is when in the upright position the stand rests on a rubber stopper I believe. If I miss that I might be in a bit of a jam. :(

From the rear tacked in place:


Another angle:


Stand in downposition:


Stand in up position:


Shown following frame in upright position:

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Steve Swan

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Looks like you are off to the beginings of a good repair !

Do you have replacement exhaust ?  If so, could bolt crank cases together, install cyl and head w/ spigots, then install exhaust w/ rubber cushion to make sure side stand strikes in desired location.


Wayne

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Nope, no exhaust Steve. I was saving that expense until the end. I was hoping a couple of triangulated measurements would give us that fiducial measuring point. Damn hard when you haven't got another bike at hand to look at!
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Steve Swan

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Since you're going to ride the bike, an option would be to source a nice set of HM300's for a reasonable price (should be very easily doable.)   Then you could toss the engine in the frame and mount the exhaust to check for proper side stand position against the rubber cushion.


Wayne

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Yes, that is an option, even if they are a damaged set. I did want to put the No # exhaust in as the final pipes. They are on sale right now, 15% off but sold out. Hopefully something will roll right here soon. On a bit of a bad roll! lol
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markb

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Wayne,
Not sure this will be much help but I snapped a couple of pictures of 1553.  The first one with the lever down shows the left side of the bracket very close to perpendicular to the frame, pretty close to what you have.


This second shot with the lever up shows a dimension of 4 3/8".  Again, pretty close to what you have.  I think you have the best idea in mounting the exhaust to confirm where it's hitting.  Looking straight down with the lever in the up position, it's pretty close to parallel with the centerline of the frame.


Here's a shot from the bottom.
« Last Edit: December 24, 2010, 10:42:17 am by markb »
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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Got an early Christmas present in the mail today. My oil tank came!  :) This one has not been compromised and appears to be in nice shape.



Clean on back as well. I don't see a Date Stamp but then I didn't on my original. Question is, do I strip this one and paint the same as the rest of the black frame items or leave it as is? It only has a few "character" marks on it in the places you would expect them.

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markb

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Nice score!  On 5383 I didn't repaint because it was in pretty good shape.  The one before that on my K0 I did have repainted but it was a pain to plug all the holes, especially the fill hole, and make sure no blasting media got in the tank.  If I were you I'd be tempted to use it as is.
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?)


Wayne

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Looking at Mark's side stand pics from 1553 above I think I'm close. I know my position is correct along the frame rail as it wasn't torn off the original re infocement on the outward side. When we ground the crap off the rear of the tab we tapped the plate back into place and took a measurement of the tab location on the frame rail. It appears we may have the angle of the tab close as well. It looks close to 90 deg. like 1553 and the measurement to the frame rail is virtually the same with the stand up.

I think the only area we may or may not be out is on the outward angle of the tab. If I knew that angle I think I would just weld this old girl up and move on. Anyone?

Here's the angle I'm looking for:
« Last Edit: December 26, 2010, 10:10:31 pm by Wayne »
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Wayne

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Found this pic over at SOHC4. I sure don't want to have this problem after paint! Looks like that angle I need will have to be pretty bang on.

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kp

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Refer: Stand in down position photo. Angle doesn't look right. Could be just the picture but just doesn't look correct.
Fellas, can someone with a bare frame help Wayne out here.
« Last Edit: December 28, 2010, 04:58:20 pm by kp »
Yabba Dabba KP


markb

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Are you talking about Wayne's or my "stand in down position photo"?  With a little luck, I might have a bare frame by the end of the weekend.
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?)


Wayne

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Mark
I hope the pic of 1553 with the stand down is correct. It doesn't look repaired unless it was all on the back side like mine was on 576. Don't feel pressured to get 1553 apart on my behalf. I have lots of other things to do like get the motor torn down.
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kp

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Sorry, I was referring to Wayne's photo posted on Decenber 22. I don't think it matters which model frame
« Last Edit: December 28, 2010, 06:32:08 pm by kp »
Yabba Dabba KP