Honda CB750 Sandcast

General Category => General Discussion => Topic started by: Wayne on November 26, 2010, 09:56:12 pm

Title: Red Dot or Blue/Green Dot on Engine
Post by: Wayne on November 26, 2010, 09:56:12 pm: I have started this thread as there seems to be a lot of theory's and general interst on the Red or Blue/Green dots found on some engine. This thread may not seem sequential at first as I am moving other posts on this topic to this thread. Please post any questions, theory's or information on these Dots in this thread only.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Joe K on November 27, 2010, 01:16:19 am: Perhaps in Wayne's case, where the dot was blue/green and the bike red, was an exception. I cannot answer for mine, because the dot was missing. I do think my bike was blue/green though because the underside of the wrinkle tank was blue/green and I think it is original. Who else can chime in on the color of the dot vs. the color of the bike if they know for sure what the original color was.

Joe K.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Riccardo on November 27, 2010, 11:02:24 am: I have elaborated and read many theories about the DOT.

Sincerely not believe that the sticher it was glue on the engines that had been repaired, also because Honda, habitually, made 3 perforations on the engineplate of the repaired motors or that they had had an action of callback.

I think that the color was really of identification of the final color of the motion, destined perhaps to two different assembly lines, one for the blue color bikes and one for the red color bike.

True being could also that the dealers they changed the dress of the dikes in order to please the customers who preferred the red bikesmotion, in fact i think that, even if today the blue appeals to a lot, in '69 perhaps age the red color more was wished.

This determined the bike with the DOT of contrasting color.

In fact I have seen more bikee red with the blu dot that not the contrary.

I agree that the dot white does not exist, is simply decolorated from the heat or the benzine or the chemicals for the washing.

I could be mistaken.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Wayne on November 27, 2010, 11:36:24 am: Quote from: riccardo on November 27, 2010, 11:02:24 am

True being could also that the dealers they changed the dress of the dikes in order to please the customers who preferred the red bikesmotion, in fact i think that, even if today the blue appeals to a lot, in '69 perhaps age the red color more was wished.

This determined the bike with the DOT of contrasting color.

Riccardo are you saying that a dealer may have changed the painted items from a red bike to a blue bike? If they have both bikes there that does not make sense to me. ??? ??? Why not just give the customer the one he wants? If you are saying they may have brought the painted items in through the parts dept. and installed them, that would be an expensive option. Lastly, if they painted the bikes there would be evidence of the original color somewhere. In my case that is a negative. It has original candy red everywhere. I think the jury is still out on this one.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Riccardo on November 27, 2010, 12:07:02 pm: Waine i not refer to the repaint of the bike.
I think that the dealers had in stock also the other colour and when a client was asking for a diferrent colour and they not had the bike in stock, they change all parts to satisfy the client.
This can generate the non match dot colour vs/colour bike.
It's only an opinion.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: kp on November 27, 2010, 08:43:10 pm: My opinion (and it's only that as I really don't know) is that the dot was placed on the engines after assembly but before they were fitted into a bike. Probably to identify what color the bike should be. The Sandies only came in 2 colors and this could be the reason we don't see other dot colors. What was assembled first, front end with motor or front end without motor. I think it was more to do with the headlight ear assembly. My view would be that the tank, sidecovers and headlight would have been close to the final parts fitted so the assumption is the dot was to identify what headlight ears had to be installed given the forks needed to be fitted prior to those later parts.
My other thoughts is that Honda abandoned the idea as they probably just needed to build them turn about, thus the dot became a redundant assembly line indicator. Just an opinion
Probably many other theories. We need an assembly line worker to sort this question out.
Calling all 1969 Honda CB750 assembly line workers 8) KP
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: cb7504 on November 29, 2010, 11:24:18 am: KP:
Your thought process is probably more correct than not as Honda was unsure at the time as to how the CB750 would sell thus the sand cast casings (cheaper) instead of die casting them (tooling = expensive). Honda wanted the market to accept their product so attention to detail was a pretty big factor, dots for color coding was probably one of the details. My two takes on the dot is: 1. ( dot relevant) for tacking purposes to keep the two production colors as even as possible. 2. (dot not relevant) produce the most popular color as per customer demand or readily available. As production progressed Honda had difficulty in keeping up with the demand. During this time some of the smaller details were probably by passed along with Honda changing over to tooling for the die cast casings. As in any business main objective was to get them off the assembly line, out the door and sold. My thoughts Marty K.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: markb on November 29, 2010, 04:36:39 pm: It seems I have to agree that my "white" dot was probably most likely red (the original bike color). So should it be restored? Have any members done this? Any suggestions on how to do this?

Riccardo had mentioned on my 97 thread that maybe someone could contact Bob Jameson to see if he could shed light on this mystery. I know who he is but this seems like a great idea for someone who actually knows him to contact him.

Mark
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Wayne on November 29, 2010, 06:38:41 pm: I want to have the Dot on my restored bike but I don't want a Blue bike! :( Darn, these details are going to make me gray!

Seriously though. If anyone's Dot is showing better than what Mark and I have posted some pictures would be nice. It would be nice to get an idea of the shades used in the Red or Blue/Green Dots.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Riccardo on November 30, 2010, 12:49:18 am: Waine,
please, post the exact size in millimeters.
I'll try to do a repro.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Joe K on November 30, 2010, 10:54:13 am: Wanye,

Just put a red dot on your engine and paint the bike red like you want. I don't think anybody could ever find out if the bike was blue by tracking the VIN. Except for all of us sandcast enthusiasts! : )

Joe K.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Wayne on November 30, 2010, 11:01:41 am: Quote from: Joe K on November 30, 2010, 10:54:13 am
Wanye,

Just put a red dot on your engine and paint the bike red like you want. I don't think anybody could ever find out if the bike was blue by tracking the VIN. Except for all of us sandcast enthusiasts! : )

Joe K.

ahhh, but Joe. No one has convinced me yet that the bike ever was Blue. :) The original owner says Red, the painted items all show evidence of Red. I may have to track down the old Dealer owner and see if he remembers selling this bike. I don't imagine he sold many, if any more. It was a small town Dealer. Couls be it came from the Factory with a Blue Dot, Red paint.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Riccardo on November 30, 2010, 01:01:11 pm: Joe and Wayne,
Should be beautiful to find the main file of the production line:
Vin/engine no./colour/delivery date.
In this way we can have a very real Vin directory to know or to do pure bikes.
But this is a Dream, as our Honda.
So called DREAM
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Wayne on November 30, 2010, 01:04:05 pm: Quote from: riccardo on November 30, 2010, 12:49:18 am
Waine,
please, post the exact size in millimeters.
I'll try to do a repro.

Riccardo
I'm going to say 19 mm.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: markb on November 30, 2010, 01:10:43 pm: Riccardo,
I would be interested in one too. Mine is probably the same as Wayne's but I'll measure mine tonight.
Mark
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Wayne on November 30, 2010, 01:20:55 pm: Could it be that the DOT is actually relevant to the Main Bearings used in that engine? Black, Brown, Green Yellow?

When I get mine apart I'll check to see if the main's are Green like mt DOT.

Does anyone have a DOT CLEARLY showing a different color? Please post pic's.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Riccardo on November 30, 2010, 04:50:49 pm: No, i dont think this.
Maybe?
But, Wayne, good luck when you'll unassemble the engine.
I dont was able to find the original bearing colour.
Also the match on the cranckase bearing was very difficult because the strange signs on the crankshaft are not easy to find and the match with the letters stamped on front of cranckcase is difficult.
But, reading the shop manual, is possible to reassemble the engine with standard bearings.
I used the standard bearings.
The engines of mine 2 restored (737 and 1256) runs great up to 8500 rpm, and over :P :P :P
Over 5000 rpm the lotus root sounds great and at 8000 is very music, an extasy.
Sorry if i'm gone out of the subject of this thread.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: markb on November 30, 2010, 06:19:15 pm: Quote from: Wayne on November 30, 2010, 01:04:05 pm
Quote from: riccardo on November 30, 2010, 12:49:18 am
Waine,
please, post the exact size in millimeters.
I'll try to do a repro.

Riccardo
I'm going to say 19 mm.
Mine is 19mm also.
Mark
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: markb on December 02, 2010, 07:12:27 pm: OK, you guys are going to love this one. I just looked for a dot on 1553, a blue/green bike. It has a red dot! And it's in a totally different place. Whaddaya think of that Wayne? There's no evidence that any of the tin has been repainted. It's engine 1789. Is it possible the engine came from another bike? More questions. What's the latest VIN with a dot? Is this another of the 88 89 distinctions? Someone should really try to contact Bob Jameson.
(http://cb750sandcastonly.com/coppermine/albums/userpics/10002/DSC05045.JPG)
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Wayne on December 02, 2010, 07:42:50 pm: You have a red dot on a blue bike. I have a blue/green dot on a red bike. Maybe we should switch engines. ;) I'm becoming less convinced it has anything to do with bike color and more with the engine itself. Hopefully when I get mine torn down there will be some trace color left on the engine bearings. I'll have them under the magnifying glass and lamp if I have to. I have been reading that some color may remain on the edges of the bearings if you look closely.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: markb on December 02, 2010, 08:37:08 pm: Yes, I've been thinking about that too. What difference would it make what color bike the engine went in? And now I'm not so sure that #97 might be white. By the way, what happened to the pic?
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Wayne on December 02, 2010, 09:01:40 pm: I put another ticket in on the pic thing. Since StartLogic had server problem last week the image software they use hasn't worked properly at all. I'm getting quite frustrated with it!
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Wayne on December 03, 2010, 02:56:18 pm: Quote from: mark1b on December 02, 2010, 08:37:08 pm
And now I'm not so sure that #97 might be white.

White would not be an option from a bearing size perspective. Black, brown, green or yellow. You sure that Red dot isn't a weather faded brown Mark?

I was going to save pic's of the Vic World 445 mile bike that sold on Ebay and didn't. :( He had a lot of pics on the auction. Thought maybe one of them would show the Dot!
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: hondasan on December 04, 2010, 02:28:30 pm: I have owned 5 sandcast bikes, and two "spare" motors over the years. All came to the UK from the US (various States). Not one of them has had a dot of any colour that I recall?

Chris R.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Steve Swan on December 04, 2010, 05:01:02 pm: The six engines i've owned/seen not a one has the dot or a trace of a dot.

Thinking not all engines had these dots.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: markb on December 05, 2010, 10:15:07 am: Either that or they came off during cleaning. I was speculating it might have been a regional thing but I have a copy of the original title for 1553 and it was a US bike and obviously some US bikes didn't have them. ???
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Wayne on December 05, 2010, 11:01:08 am: I was thinking maybe some folks took them off not wanting a big colored "bingo dabber" on their motor. ???
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Steve Swan on December 05, 2010, 11:31:21 am: I've owned six engines and i have not seen these dots on any of the six. I did see one of these dots on an engine somewhere, i think it was at the 2009 Meet.

Is the dot paper or plastic ?

Is the dot a glob of paint ?

How is the dot held to engine ? i.e., Does the dot remove easily or does it take deliberate effort to remove the dot ? i.e., is the dot held on w/ weak or strong adhesive or something other than adhesive ? Is the dot readily perishable ?

It's difficult to believe the dots specify chassis parts colours, considering we have red bikes w/ blue dots and visa versa.

If one looks at the Honda Service Bulletins (SB #14) Honda had their own system of identifying rod and main journal bearings. The different main bearing sizes were color coded brown, black, green and yellow as well as using an "A-B-C" lettering system.

Because Honda had a system for denoting bearing sizes, i think it's difficult to support the idea dots were fixed to the outside of the engine to denote bearing sizes.

What i find interesting is the fact that we have ony found only two dot colours. It appears the color of the dot was subject to fade, as evidenced by Mark's dot.

What's also interesting is the fact that not all engines have this dot nor do the engines w/o this dot have any trace of a dot ever having been present. It would be good to verify if all engines had a dot - OR NOT.

Just my 2 cents worth.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Wayne on December 05, 2010, 02:58:25 pm: I used a heat gun and raised a section of my Dot. The adhesive did not lift from the aluminum block and appears very strong over time. The separation took place between the adhesive and what appears to be plastic. Again it is quite brittle, feels like paper but has strength like a thin piece of plastic.

Another thought entered my mind as I was leaning over the old girl. Is it possible that during the early days of assemble they had to have a pass / fail process for engines to go to the marriage station? (where the motor meets the frame) Perhaps Red Dot engines got sidelined for a tweak or two and then onto their designated mate?? I guess we could come up with all kinds of theory's on this one. We need an inside worker!
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: kp on April 14, 2011, 03:17:56 pm: Speaking again about these dots. This is now the second time I've seen this and it relates to the "DOT" being found on the carb rack. My VIN11970 has a blue dot on one of the outer carbs. I had forgotten about it and did not even link the engine dot and these carb dots. I have now come to the realisation that they are one and the same. This dot is exactly the same as is on my K0 and is seen on a K0 carb set for sale on eBay
http://cgi.ebay.com.au/CB-CB750-CB750K0-CARBS-K0-CARBS-CB750-CARBURETORS-/160573584677?pt=Motorcycles_Parts_Accessories&hash=item2562ee7525 (http://cgi.ebay.com.au/CB-CB750-CB750K0-CARBS-K0-CARBS-CB750-CARBURETORS-/160573584677?pt=Motorcycles_Parts_Accessories&hash=item2562ee7525)

Methinks this is interesting and still a mystery.

(http://cb750k0only.com/coppermine/albums/userpics/10003/_28KGrHqZ2C21k4E2ERPHGOnBNp29nv28kBw7E7E_125B15D.jpg)
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Riccardo on April 14, 2011, 04:10:08 pm: Nooooo, I cannot believe to this.
I truly am astonished.
Are two years that we all break off the head on the red or blue dot.
And now?
We find it on the carburetors!
To this point we need Only a time machine in order to back in 1969.
And if the previous owner has moved it on the carburetors because it did not appeal it on the engine??Where we will find the next time to it?
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: mrhonda2u on June 14, 2011, 05:52:57 am: I have just purchased Sandcast #3034 With a little over 5,000 original miles. The bike has a blue sticker with red paint. This was owned by someone that was deeply involed in woodstock in1969 and the bike was at woodstock.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Riccardo on June 14, 2011, 12:16:00 pm: Hi,

post the photo of the bike please, we want the emotion like you.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: tomcourtney on November 06, 2012, 10:41:59 pm: First let me state i dont know.... but could it be the different assembly plant as in the link below, it says that the Hamamatsu and the siatama plants were converted for the CB750 model in 1969 Maybe? TC

http://translate.googleusercontent.com/translate_c?depth=1&hl=en&ie=UTF8&prev=_t&rurl=translate.google.com&sl=es&tl=en&u=http://www.fazermotos.com.ar/historia/Honda-750-Four.htm&usg=ALkJrhjxUfPmeqiojb-nzAWLeKn1Sgp0Fw (http://translate.googleusercontent.com/translate_c?depth=1&hl=en&ie=UTF8&prev=_t&rurl=translate.google.com&sl=es&tl=en&u=http://www.fazermotos.com.ar/historia/Honda-750-Four.htm&usg=ALkJrhjxUfPmeqiojb-nzAWLeKn1Sgp0Fw)
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Garry32 on August 27, 2015, 07:15:23 am: Hi This is my blue dot from my cases it is directly under the air box number 40:: unrestored sandcast
:)
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: DW69K0 on August 30, 2015, 08:20:50 am: Gary-
I have a blue dot in the exact location on unmolested E1685. Like yours, mine has good color. Is your Sandcast candy blue green?
DW
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Garry32 on August 30, 2015, 09:10:53 am: Hi DW yes it was candy blue green blue green, But when I bought the sandcast the seller had put candy red tin ware on as they where in better condition. I am just in the process of buying the caddy blue items if
He will part with them.
Garry :)
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: DW69K0 on August 30, 2015, 10:05:37 am: Best of luck!
DW
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: 4pots1969 on May 24, 2017, 03:11:48 pm: Hello everyone, Here is a K0 with a frame number 1020280, dated January 1970 imported from the USA and it has a green pellet glued on carburetors...I thought it might be interesting
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Steve Swan on May 24, 2017, 08:42:23 pm: green dot on gold bike kind of shoots the theory of colored dots used to designate body color......
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: 4pots1969 on May 25, 2017, 03:57:00 am: Why not have indicated the colors by a red dot, a blue dot, and a yellow dot?? We have never seen these points of color on the French bikes... Very dubious on this theory...
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Steve Swan on May 25, 2017, 10:01:28 am: i would suggest the color of the dot might be immaterial. i would suggest the dot meant the motorcycle passed a final inspection, after the bike came off the assembly line. i would suggest the dot indicated the motorcycle could be put in a crate, ready to be shipped from the factory.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Steve Swan on May 25, 2017, 10:55:30 am: in an earlier post, someone suggested the dot might indicate which factory the bike originated from. this could be a plausible theory.

who knows how many factories produced the CB750 in 1969 ?

so far, we have identified 2 colors for these dots ?

and, we have identified motorcycles that have no sign of ever having a dot ?
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: DW69K0 on May 25, 2017, 08:30:33 pm: My personal belief is that the dots were place on the bike as an indicator of a problem that was found during testing that needed additional corrections during quality checks before leaving the factory. I don't have any specific information to back up my theory, but I do own two Sandcasts with blue dots close to the top casting date.
DW
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: DW69K0 on February 18, 2018, 10:45:56 am: Quote from: Garry32 on August 27, 2015, 07:15:23 am
Hi This is my blue dot from my cases it is directly under the air box number 40:: unrestored sandcast
:)

The engine dot topic is still intriguing and mysterious.

Friday night I received a new Sandcast from CA, and during examination and documention process yesterday I discovered another Blue Engine Dot. The blue engine dot is on a Ruby red bike. This now make three engines in my possession that contain the blue dots at different Vin ranges in the exact location as Gary's photograph shows in his earlier post.
I am fully convinced that these were not placed on every engine and had to specifically call out a process or were used to bring attention to some feature or issue during assembly.
The dots are definitely made from a very hardy material as the dot survives well in the location and retains good colors after almost 50 years of environmental exposure.
My theory still stands that the dots indicated an issue during inspection, but I don't have any evidence or facts to back it up. Maybe we will will learn more as time passes, this seems to be lingering as another Sandcast mystery.

Best,
DW
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Steve Swan on February 18, 2018, 11:12:06 am: Duane, thanks for posting your findings on another dot finding. I believe your theory is a good one.
Title: Re: Red Dot or Blue/Green Dot on Engine
Post by: Ssicbx on September 22, 2021, 09:35:05 am: Reading this thread yesterday I was thinking if I saw any of these dots on my bikes I had in the 70's. I'm now 68 and that was a long time ago. Anyway I woke up this morning thinking about these dots and said I have dots on my K4. Does this count? Red dots on carbs.