Red Dot or Blue/Green Dot on Engine

[Wayne]

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.

[Riccardo]

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
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.

[markb]

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

[markb]

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.

[Wayne]

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.

[markb]

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?

[Wayne]

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!

[Wayne]

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!

[hondasan]

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.

[Steve Swan]

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.

[markb]

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.

[Wayne]

I was thinking maybe some folks took them off not wanting a big colored "bingo dabber" on their motor. 

[Steve Swan]

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.

[Wayne]

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!

[kp]

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

Methinks this is interesting and still a mystery.