Restoration of Sandcast #97

[Steve Swan]

nice work Mark!  perfect place for a helicoil.

[markb]

Well, things were going good. I got the camshaft holders and cam installed and when I torqued the 56mm screws for the caps three out of four of them stripped out.   It’s the holes with the pins (circled in red).


So the head is back off. Three steps forward, two steps back. These are going to be a little bit trickier because of the counter bore for the pin. Fortunately the O.D. of the Heli-coil is smaller than the 8mm pin hole. Not much choice as to what kind of insert to use here.

Some of you may be thinking that I’m maybe just over torqueing the screws. They weren’t even close when they let go. To make sure I checked my torque wrench and it is right on. Below is a picture of my method.


This is the first time assembling this cylinder and head since they came apart. And you probably recall that they came apart hard. I’m guessing the threads were damaged then. The other thing is that the 56mm screws could be a little longer. In fact on later K0s the screw is a 60mm. If you subtract the washer and the thickness of the holder and cap and the 8mm depth of the pin hole and actual length of the screw you’re lucky to have 8mm of thread engagement. With a 60mm screw in would be 12mm engagement which would be a significant improvement.

I’m also going to be checking all of the tapped holes for the valve cover before I put the head back on.

[Steve Swan]

Mark, i know the sick feeling when one feels the "purchase" of fastener letting go....!  it just happens; for anyone who has worked with this old metal, it is the inherent nature of the work.  you are working with 50 year old materials that have been subjected to stresses and strains of use, misuse, abuse and disuse we know little to nothing about.  i have interesting stories working with 90 and 92 year old materials (helping local buddy get his '29 together and i am building a second '27 for myself).

[markb]

I’m almost ready to put the engine back in the frame. 


I Heli-coiled the holes with the pins under the cam holders. As long as I had to do it I did all four. Then I assembled the cam towers before mounting the head to make sure everything else would torque down. I also checked the valve cover. I’m glad I did. I had three of the 63mm pan head screws that were about 0.5mm from tightening, even with the gasket. Almost didn’t notice it. I thought they were tight but they were bottoming out in the tapped holes. I thought about just regrinding the screws down for those holes but if and when it comes apart again it might not be noticed. Just the kind of stuff that previous owners do to mess us up. I was able to run a tap in those holes and get just enough thread. I checked the cam chain tensioner too. I stripped out a hole for that years ago (and I Heli-coiled it). The early parts book calls out a 36mm screw and later it was changed to 40mm. I checked and there wasn’t much of the screw sticking out with the 36mm. The tapped holes were just deep enough to use the 40mm screws. So I decided it was better to be safe than correct.

I got my rubber inserts for the fins. Thanks again Chris. Just started putting them in when I ran out of gas. They go in pretty tight. The last thing I want to chance is cracking a fin. I think I’m going to trying heating them or boiling them in water to soften them up a bit.

[42barab]

Mark


Was the softening process successful?

John

[markb]

It didn't help much, if at all. I ended up using a little bit of Sil-glyde on the top and bottom to help them slide in better. Still plenty of work, but there in.

[markb]

As of yesterday she is finally together again. Once I got the engine together things went pretty good. So now in addition to the original cases it has the original cylinders and head along with the original valve cover.

I also found that the front brake was sticking so I had to pull the caliper apart and while I was at it I cleaned up the master cylinder and flushed the rest of the system. It had sat for quite a while. Works good now.


Here’s some pics of my setup for installing the engine.


Of course it helps to have a nice hoist.


Start to finish about 45 minutes and no nicks.


And I forgot to mention I now have the correct spoke nipples installed. I have a few more details to correct but she’s getting close to being as correct as humanly possible.

[42barab]

Mark

Nice workshop!!  With room to expand.   John

[kp]

Yes I was thinking the same thing.

[sandguss]

hello Mark,

excellent Job, great resto

Manfred

[4pots1969]

Hello Mark
You do not have the right cap oil on the photo that is a 14 mm on your engine, while it should be in 17 mm, and it seems to me also from memory that your regulator has a sticker for references while they must be painted, and also that your oil pan drain plug is too recent, it must be the same as the oil tank drain plug...
I also think that your rear shock absorbers are not original Honda, because they are marked CB750 3.F.05 in black in the bottom near the fixing screw, which corresponds normally to CMS reproductions, they must also have a small hole of about a millimeter behind to be Honda originals... The copies from CMS do not have this little hole behind if you look at the second picture in the link...
But maybe you have rectified the "errors" since... So in this case ignore it, because it was just to help you achieve perfection !!  

https://www.cmsnl.com/honda-cb750k0-four-1969-usa_model14346/cushion-set-rear-non_05240300010xw/#.XE8LVdThDyk

[markb]

Nice workshop!!  With room to expand.   John

Thanks. It's actually my company's shop. I'm very lucky to have an area where I can work on the bikes and have all the other resources available to me as well.

[markb]

Hello Mark
You do not have the right cap oil on the photo that is a 14 mm on your engine, while it should be in 17 mm, and it seems to me also from memory that your regulator has a sticker for references while they must be painted, and also that your oil pan drain plug is too recent, it must be the same as the oil tank drain plug...
I also think that your rear shock absorbers are not original Honda, because they are marked CB750 3.F.05 in black in the bottom near the fixing screw, which corresponds normally to CMS reproductions, they must also have a small hole of about a millimeter behind to be Honda originals... The copies from CMS do not have this little hole behind if you look at the second picture in the link...
But maybe you have rectified the "errors" since... So in this case ignore it, because it was just to help you achieve perfection !!  

Thank you for your observations. I will definitely check into them. This is why I post, so I can learn. What do you mean by regulator?

You are correct that the shock absorbers are repros. I have originals that I haven't gotten around to restoring. There are some other flaws that I plan to correct at some point too.

[4pots1969]

Regulator ref : 31400-300-035

[markb]

Ah...voltage regulator.  Yes, I'm a little hesitant to use 50-year old electrics. Now I haven't yet tried to start it but I would like to. If I have new parts (like coils, etc.) the odds are better that it will run and if not it shouldn't take as long to trouble shoot.