Restoration of Sandcast #97

[markb]

I have my “spare” frame torn down and side by side with #97 frame.  You can see that the side stand bracket is definitely in the wrong place.


So while I had both frames up on the bench I decided to compare them closely.  Good thing I did.  First thing I saw was there are some spacers missing on the bottom side of where the rear fender mounts.  Here’s what it should look like.


Here’s what I have (don’t have) on #97.  It looks like they used to be there.  I don’t know why or how they would be removed but I pretty sure they should be there.  Anyone think not?  I can machine up some spacers and have them welded in.


Then I noticed the horn mount.  This is what I think it should look like.  The mount is basically perpendicular to the frame.


Here’s what’s on #97.  It appears to be bent forward.


Here’s a shot from the bottom on the spare.


Here’s a shot from the bottom on #97.  Here you can also see the gusset has been dinged on the right side, maybe from the same incident.  Who knows?


I’m only assuming the horn mount on #97 is bent.  One of them is probably wrong.  I’d like to get some feed back to confirm this.
Thanks,
Mark

[markb]

Any tips on getting the flat head screws out of the back side of the rotor?  They appear to be peened to lock them in place.  I think on my K0 I just drilled the heads off and replaced the screws.

[markb]

Another question.  Is the hole that’s at an angle to the through hole in the rod journal supposed to go all the way into the through hole?  If so, does anyone know what size hole?  I used a drill bit by hand to clear out the through hole in the journal.  After doing one this way I used an electric drill.  They were caked up pretty hard.  The same sized drill stops at about a ¼” into the angled hole.  By the way, the journals aren’t as bad as they look.  They’re discolored but there is no scoring or noticeable wear.  When I run my finger across it I can’t feel anything.

[hondasan]

Yes, that angled hole should go all the way to the journal cross-hole, and then carry on to the next "main" journal - oil is fed directly to the main bearings, but relies on being able to feed through the angled crank drillings to get to the big end bearings. At least with these early cranks you can remove the blanking screw - some have flat bit heads, some hexagon key heads - whereas later cranks are blanked off by steel balls pressed / peened in place. Unfortuantely, can't remember the drill bit size I have used to clear them out. Start with a small one and go up in size slowly. It may be that if the drill you have tried first is too large, and at 1/4" it has reached the bottom of the threaded hole, the actual oil hole being of a smaller bore.

Cheers - Chris R.

[markb]

Once I cleaned the sludge out of the angled hole I see now that there is a set screw there with a hex socket.  Obviously I am going to have to get them out to make sure there's no blockage in the oil paths.  Oh boy. 

[ashimotok0]

Are you re-using that crank Mark It may just be the photo but it looks a bit too far gone, to me. I did see someone on Ebay in Australia selling undersize shells (0.25mm from memory) for the 750/CBX1000 and he claimed that the depth of hardening of the journals would allow the regrind. Cranks are so cheap in the US though, so probably a waste of time regrinding even if possible.

Cheers Ash

[markb]

I am hoping to use the crank mainly because it has the correct 10mm rotor bolt hole.  I'm guessing it would be hard to find a replacement.  I know it looks rough but if I can get the set screws out I think it's salvageable.  I've got it soaking in the rust remover right now.  Like I said the journals don't have any galling just discoloration.  I'll check them with a micrometer to make sure they're not worn undersize. 

[markb]

I cleaned up the crank a bit more and tried removing the set screws.  No luck yet but I don't want to strip out the socket.  Maybe worse news though.  After cleaning I can see the main journal next to the rotor is pitted.  It's in the middle of the journal and not very deep but cause for concern.  What are my options?
1. Replace it with a decent 12mm rotor bolt crank from a later unit (probably 1553).  Will this reduce the value, how much?

2. Try to find another 10mm rotor bolt crank.  Anyone have one?

3. Get this one repaired.  I've heard of a process where they build it up and regrind.  Anyone heard of it?  And the undersize shells might be an option.  .25mm is about .010" and I'd be surprised if the hardness didn't go deeper than that.  But what does that do to the value?

4. Use it.  If I do this are we talking it may go 10,000 miles instead of 100,000 miles or something worse?  The reality is it's not likely that I would even put 1000 miles on it.  And as far as the value goes, I'm not planning on selling it anytime soon but someday it willl be sold and I'd like it to be as desirable as possible.

Of course if I don't get the set screws out it's not going in no matter what.  The cross holes in the rod journals were completely plugged (and it wasn't soft) so there's no reason to think the angle holes aren't plugged too.  I could sure use some feedback on this one to help think it through.

[Steve Swan]

First off, will ultrasonic clean the passage ways ?  Seems to be to me the method of choice since it is "non-invasive" and "non-assaultive" to the crank.  I'd suggest doing an internet search, look for a high end autmotive restoration business and ask them their experience.  Your crankshaft is not the first shaft to be in this condition and not be saved.  20 miles from here we have a world prestigous Bugatti restoration service, if you know anything about classic Bugatti's they are some of the most valued and  expensive antique cars in the world.  I would suggest contacting these guys and if they cannot advise you, then ask them who can - http://highmountainclassics.com/  In order to clear those passage ways, it may take repeated treatments of whatever the best procedure is, which i believe could be ultrasonic, until told otherwise by an experienced expert.  Honestly, i cannot imagine you will have any luck removing those plugs that were used by the factory to block drilling access in order to drill these passageways at the factory.  Those plugs not only were Loctited in, but they have decades of rust to make them a permanent unmoveable part.  You may want to contact Mark McGrew at M3 Racing for suggestions, i would say Mark is the best CB750 expert in the USA, if not the world - http://www.m3racing.com/  You have to have these passageways clean before you can consider saving the crank journals.  All my opinion.

The main and rod bearing inserts come in four (4) factory undersizes.  The question is, can the journals be ground to "clean up" to a factory recommended undersize ?  If so, no problem.  Otherwise, you will have to consider finding replacement 10mm shaft or having 97's crank built up and then turned down to chosen undersize which is typical machine and engine rebuilding procedure.   I have always heard from old and long time experienced engine builders isolated pitting of a journal does not matter as long as the crank can be turned to an undersize to fit the bearing shell.  The pitted area acts as an oil pocket, provides additional cushion when filled with oil and does not affect serviceability of the journal or longevity of the engine.  The crank is a 5 main bearing shaft, over-engineered to not fail, sothis pitting, especially on an end journal is not any appreciable concern.

Myself, i would not be concerned with what is done to repair the "10mm shaft" relative to value of the restoration.  These repairs are all hidden and factory recommended, with exception to replacing the 10mm shaft with a 12mm bolt type shaft.  The only concern i would have, would be the same as yours, it would be nice to save the 10mm shaft, because in the event the 10mm bolt was exposed, the correct 10mm bolt would be present.  I'd suggest calling my engine builder, he is a REAL pro, he will know who can build the shaft up (if required) and he can turn the crank down.  His name is Tom Wirth, his number is 608.493.4300, he is outside of Madison, Wisconsin.  If you call Tom, tell him how you learned of his name.  He is just finishing "buttoning up" my E2241 for 2157.

Just my 2 cents worth.  

[ashimotok0]

I am not a Sandcast owner so no really qualified to speak here but I would just fit a a later crank. What does Vic World do? I can't imagine he has a stash of NOS early cranks or does he? DSS has a new crank at 450GBP but doubt it is a really early one and of course mega expensive.

The rods may be a different story though because I read somewhere that they were very closely matched so that there was minimal vibration (hence the coin on the seat not falling off demo)

How about this - its described as 1970 but I reckon the build date is Oct 1969. It is about 20 VINs from my K0 1010382 Oct 69 K0. As I say though I don't really know much about Sandcast cranks and I guess they must have had a smaller Ø rotor bolt. Mine did have small slotted head blanking screws though and not balls to seal the drill holes and the rods had the Japanese Hyroglyphics markings and were of the early profile around the big ends. Could you use some kind of insert to reduce the 12mm down to 10mm. Having said this Honda will have increased the bolt size for added reliability IMHO. Could you havea special rotor bolt made with 12mm thread which replicates the head of the 10mm one?

I wonder what Vic World does about some of the features, which were unique to the Sandcast, but were subject to safety related modifications such as:-

 http://data.sohc4.net/SB750/750_15.pdf

Links to early crank sales but not 10mm bolt size

http://cgi.ebay.com/ebaymotors/CRANKSHAFT-CRANK-K0-1970-HONDA-CB750-CB-750-69-70-71-72-_W0QQcmdZViewItemQQhashZitem53dc992320QQitemZ360183309088QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_906wt_742

Or this possibly

http://cgi.ebay.com/ebaymotors/Honda-CB750-CB-750-KO-0307-Crankshaft-Crank-Shaft-_W0QQcmdZViewItemQQhashZitem53e5879f63QQitemZ360333156195QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_500wt_759

[Riccardo]

Mark,

i purchsed recently from DSS some parts with little damages but NOS, and i've seen that they one crackstaft.

They had had great courtesy with me, sending also the pics before the purchasing.

Ask via email, surely they will anwer you with a fhoto and you will see if the crankshaft is really "early".

[Steve Swan]

I'm not suggesting save orignal shaft over a replacment, but if there is no choice or if one want to save the crank, then those were my thoughts.  Myself, i'd check into saving the shaft while at the same time looking for a replacement as well as consider a 12mm, just to keep all my options open until the doors started closing on options.  It is possible 97's crank may not be able to be saved, BUT it never hurts to find and learn as much information as one can, to affect a save.  Obviously, a suitable replacement is the ideal solution.  Even if a 12mm shaft was used, i don't feel it would really be any real issue at all.  Mark, don't forget i have a good 12mm shaft i offered you a while back !  You can have it for the asking if that is the route you decide to take   

[markb]

Thank all you guys for your great comments.  I feel better than I did last night, somewhere in here there's a solution.  I've heard of Mark McGrew and Tom Wirth and both aren't all that far from me (I'm in the Minneapolis area).  There's another local motorcycle machine shop guy, Bill Bune, that has done some work for me and he's only 20 minutes away and he does crankshaft repair.  I don't know why I didn't think of him last night.  I think the first thing I'm going to do, intead of sitting here just scratching my head wondering what to do, is bring it to an expert (not that you guys aren't knowledgeable) so he can actually see it and give me a recommendation.
Steve, you're right about the oil galleries.  Unless they can be cleaned out it can't be used.  The problem is if you can't get the set screws out how do you know they're clean?  It's a long ways from the main journal to the rod journal and there's no way to inspect it.  The ultrasonic might clean it out but the cross holes were plugged completely solid.  When I ran the drill in the hole it was like drilling a piece of hardwood and came out in the form of a dry powder.
Anyway, it's time for me to quit worrying about it until I get some questions answered.  I'm going to talk to Bill first and then maybe call Mark or Tom too.
Thanks again guys,
Mark

[markb]

I got so involved with the crank that I forgot about my frame problems.  I'm dropping the frames off this Friday to fix the side stand mount but just want to get an opinion about the posts on the bottom side of rear fender mount and the horn bracket.  Any agreement that the 97 frame is wrong on these points?  I could probably straighten the horn bracket after but this guy is kind of a welder/fabricator and I'd like to have him fix that too.  And I'd like to machine up the spacers before hand.  I feel like I'm being a pest but I'm really trying to do this right.
Thanks,
Mark

[Steve Swan]

Realilty can be a bitch, but then sensibility sets in.  As you say Mark, "It's time for me to quit worrying about it until I get some questions answered.  I'm going to talk to Bill first."

As far as checking patency of oil galleries, i would have to examine the shaft i have, then offer possible suggestions, ASSUMING the "concrete debris" in your galleries can be removed.  I would think it's possible to check gallery patency from gallery opening to gallery opening using high pressure compressed air.......... after the cleaning procedure has been completed.