Found A 1969 - What to Look For?

[Wayne]

Steve
You said those plastic parts were made "nasty, rotten, brittle material. Has the material been identified here? It tests like polyurethane but I could be wrong. I had a friend who had a better sniffer than me who could tell me but he's no longer around. I see three types of repro side covers. Fibreglass reinforced panels, ABS and polyurethane. It would appear the latter would be a better choice for a more "autentic" build if I'm correct on the original substrate.

[Bickle]

Hi
I would definitely restore the airbox...if just for the provenance or showing.....not sure what your intentions are.....but if you plan on riding it get a set of repro's for riding. That's what I do.
Steve

[Wayne]

Goodness, another Steve! Yes, I agree Steve. I have been doing a lot of reading, and whether I restore this bike or sell it to someone else I think the original parts should be salvaged and repaired where possibe, especially the early air intake box. As for the side covers from a collector point of view is it better to have the originals repaired and re-finished or purchase the best repros money can buy? I would imagine finding NOS or even near perfect used covers would be almost impossible. These are the things I will look at over the next while and make my decison on what to do with the bike after I finish my fact finding. Thanks for chiming in Steve. I'm here to learn.

[Steve Swan]

Hi

If the material the headlight shell, side covers and airbox are made of polyurethane, it's not the PUR i am familiar with. That being said, i am no plastics expert, but this material Honda used seems more brittle than flexible and cracks fairly easily when used. I am not aware PUR has these characteristics and the PUR i am familiar with does not degrade with age like the material used by Honda.

I agree w/ Steve F on saving the airbox, best suited a good shelf item or fit for a museum bike. Getting that restored orginal airbox assembled and mounted in place without breaking it in the process is entirely possible, but the stress of being mounted, heat and gasoline vapors will likely make it crack in time. Wes Anderson told the story of just bringing his long stored sandcast machine into the warm daylight sun, came back and there were large cracks in the box.

I am not aware the "nasty, rotten, brittle" material has been identified. A very reliable, knowledgeable body man i know, was unable to say what the material is.

NOS sidecovers are *not* impossible to find in the desired color, "only" about $500 for a set and a NOS early airbox will be a long time a findin' - likely never. Even if one decides to buy a set of NOS covers, then are you going to be able to live with the ink stamp date ? e.g., 548 likley built April 69. Pretty certain bet NOS side covers will have an ink stamp date well later into 1969, even 1970. I have heard details like this drive purists mad.......... 

So, therefore, to my way of thinking, one is pretty much relegated to using repro body parts, unless one is lucky enough to have a bike with solid original body parts -or- has access to a cache' of NOS OEM parts that have the appropriate ink date stamp to month/year of a particular machine's manufacture.........

The material the Japanese used is not fibre glass. Nor are there markings on CB750's such as used by inspectors on automobile assembly lines. About the only 'inspection' marks on a CB750 that i am aware of are the ink date stampings on body parts *and* on inside of engine covers and cases. The other assembly completion marking i am aware of are the yellow paint dobs on certain nut and bolts. Further, i am not certain Honda was dabbing yellow paint on the sandcast machines, it is possible this yellow paint dobbing came along after sandcast production era. I am not aware of anyone who has the exact font to replicate the font of the stamp used on these sidecovers.

Seems, with this sandcast restoration 'business', there are always compromises to be made in the consdiderations to replicate "original."

[Wayne]

Yes Steve, I understand what you're saying on the polyurethane. It certainly doesn't have the characteristics I have seen in a polyurethane product used today. It does however fall into that category when I do a burn test on it:

It melts when touhed by an orange hot object so it is a Thermoplastic.

It burns (yellow flame) and ignites in seconds. (less than 10)

It does not drip while burning. (I didn't test with a large piece though)

Black, almost sooty smoke

The smell of the smoke is nondescript.

To my knowledge those are characteristics of the polyurethane family.

Like I said, I may well be wrong and the melt/burn/sniff test is not perfect. My old friend was far more skilled at it than I. My last years working were with one of the major auto makers and I worked in the body electrical area, working closely with engineering. I was onthe technical side and kind of fed the problems over to them. I'm not even sure who is left up there but I might make a call and see if they still run a lab in Canada. If they do maybe I can get this stuff analyzed. I agree, it's a strange substrate and it will bug me if I don't find out what the heck it is! I thought it was like bakelite at first, until it melted! I'll see what I can do.

[Steve Swan]

Wayne,

Thanks for the informative post !

Will be great to hear more from you.

I appreciate your enthusiasm for research

Like i said, i am no plastics expert. Certainly this old material could be a PUR substrate.

I only have some experience with PUR used over th past 10 years, including some PUR welding, but beyond this, nothing more.

[kp]

Side covers get my vote as made from ABS. My painter, now retired did mine and was a long time plastic welder, probably one of the first around in my town. He did some crack repairs for me and immediately identified the material as ABS. His specialty was bike repair and painting and told many stories about different plastics used in fairings etc. Many of the later bike fairings could not be plastic welded and one he mentioned couldn't be welded or glued. But I do remember being very adamant about the side cover material being ABS. I think the chain guard was nylon. KP
PS. These are good discussions

[Wayne]

It could be ABS. ABS will drip when burned. This did not but like I said, I only tested a small piece so maybe it wasn't a valid burn. The smell from burning ABS is Acrid. I didn't find this acrid at all but then again, my sniffer isn't the best! ABS will burn yellow with blue edges. I tried three times as I was looking for this. No blue.

That's not saying the boys at Honda didn't come up with some kind of ABS based substrate. With no identifying marks on plastics back then I'm guessing the only way to find out is to test. I have already sent an email to an old friend from work to see if the lab at Engineering is still operational.

Where I'm going with this is, if we figure out exactly what this stuff is then perhaps it can be better preserved. For example if a good side cover were stripped, could a chemical be applied that will re-activate the binding agents in the substrate thus bringing it back closer to it's original composition. It might be a stretch but these things aren't getting younger. I find this stuff intruiging, even if I decide not to do the restoration. I'll keep you posted.

Does anyone know where there might be a picture of an original set of sancast side covers. (inside shot, never re-finished) I'm curious as to the amount of overspray the crept to the mounting posts and the inner part of the cover. (if any)

[kp]

Mabe it was PVC he said. It's a fair number of years back but we are talking 40 years ago and what was ABS then could be chemically different today. One thing is for sure, heat and sunshine makes it very brittle and prone to cracking so maybe there is a clue in that. Manfred Doring may have a picture of the reverse side  KP 

[Steve Swan]

From what i know PUR has been around since the late 1930's.

I am sure, as Wayne has said, there have been newer and different substrates developed since PUR was first created.

From what Wayne is saying, his preliminary testing is not conclusive, but appears to support the sidecover composition has some of the characteristics of being in the PUR family, but not all the characteristics.

Considering there are different substrates, the chemicals used within the PUR family to make these sidecovers then may not be the substrate of choice used today, if Honda were still making these side covers.

[Wayne]

I have made my decision on what to do with the bike. I'm going to keep it and give it my best shot. Since I will want to ride it a bit to some local "show and shines" it won't be a perfect restoration I'm sure...but who knows once I get started! I'm already making space to keep it in my shop once it arrives on Sunday. (there was a delay getting it moved) It will probably go kind of slow as I have a custom on the go that I have to get completed. I figure I can get the Honda stripped down, tagged, photograped and documented when time permits.

I put together a quick website where I will store details of the teardown and assembly. It's not inteneded to take anything away from this site, I just have lots of server space so I thought I would put it to good use.

http://1969cb750sandcast.com

I know I will have lots of questions, the first being about frame re-finishing. I have seen some bikes powder coated, some painted and some left original. Mine will have to be refinished as the paint is off in some areas.

The guy who does my custom paint work recommended a guy who came back with what I thought was a very reasonable quote to strip and powder coat the frame. He did ask though, chemical stripping or bead blasting? Your choice.

So what are thoughts on frame finishing for the type of build I'm doing? I know powder coat is more durable but if I'm going to this length should I go with something closer to what Honda originally used?

Does anyone else have their builds documented out? I see World documeneted a one day build online but they don't talk about re-finishing tecniques in any detail. He did a nice job though!

[Steve Swan]

At VMD, Vic gave 3 one hour long seminars on restoration considerations, processes, finishes, plating, etc.

My self, never been a fan of powder coating and use it only on select applications. I know p.c. can look fantastic from a quality provider. I don't like p.c. because it WILL chip (sometimes very easily with the "tink" of a slipped wrench or stress of tightening a nut), it DOES get microfine scratches from cleaning. Of course, paint will do that as well, but at least paint has a "green" period where it will not chip or twist of as readily as p.c . Just MY experience/opinion....... !

Other than that, the outcome of the restoration is 100% in the eye of the owner/restorer. Of course, many of us have found what works besrt for us, paint finishes, plating, etc.

Wayne, just keep asking questions and then ultimately follow your desire.

GLAD TO HEAR YOU HAVE DECIDED TO KEEP THE BIKE !

[Nielsen]

I would never use PC on a classic bike. A good nomal quality painting will be good enough for a bike that not beeing used in every weather, and it looks better than PC. It will also be much better than Hondas original painting witch was bad quality without base coat.

Karsten

[Wayne]

The bike is at home in my shop! Finally! I have started to upload pictures to my web site showing the current condition of the bike, the good, the bad and the ugly. IMHO it has all of the above attributes. Nothing time and money can't fix! I have started to soak some of the fasteners with Liquid Wrench in hopes of easy removal when the time comes. I have had great luck with this product in the past.

I have corrected the numbers on my site. The bike is actually:
Frame - 1000576
Engine - 1000748

I thought the frame read 578. My apologies.

I read EVERY thread on the forum here and have learned a lot so far. Still a long way to go. I read about the engine cases paint controversy and it appeared that Vic World put that issue to bed. For the record though, 748 exhibits all kinds of engine paint still intact. The engine is corrosion free in many areas as a result.

For now, I'll get my pictures posted and we'll go from there. There seems to be a few curious things about the bike but we'll get those figured out along the way.

If there is something specific you would like to see let me know. I'm keeping the camera on charge.

Lastly, the tank appears to be in excellent condition so I have a mini web cam with led lights on the way so we can explore inside! I'll post the movie file on my site. Yes, I will fill it with an inert gas before I stick that cam in there!

Any feedback or observations are very much appreciated.

Almost forgot! The right side cover seems to be in good shape. The problem is, the rubbers are very dry and hard so the cover does not want to come off. I didn't try too hard. I sprayed some WD-40 where I could. Anything else that might help? I would hate to break a mounting tab off.

[donzie]

Wayne on some of the sidecover tabs you can reach around from the backside with one finger & push out on the tab so you don't snap it off. A little heat from a blow drier on the rubbers also helps. Do your self a favor & replace the old hard rubbers asap