eschlwc

yes, '72/'73 is older than '76.

here's are a few moto threads:

https://www.bikeforums.net/classic-vi...ght=motobecane
https://www.bikeforums.net/classic-vi...ght=motobecane
https://www.bikeforums.net/classic-vi...ght=motobecane

zola1

Just weighed the frame bare on its own 2kg ! Seems very lightweight, does this help with the model I'd ?

stevegreer

You know, I totally looked right past the word "older" and thought you were meaning "post-1976"! Haha! My apologies for that! You'll have to forgive me, I've been up since 4:00 (eastern time zone) this morning and my brain is a bit frazzled from being at work.
Thanks for posting the serial number database link! That will be some useful information.

zola1

mine is 26.6 so it indicates a Reynolds 531 Moto frame

zola1

just got back from work, i was replying to the posts via my iphone so didn't get a good look at all the replies, thank you for them, i'm going to go through them i'll post a reply later and let you know what i make of the database info, it looks really useful ..thanks

Looks like it's a 73 model picture shows a stamp below the headset, a step closer to a full I'd

Derrick

zola1

The top & bottom head lugs have a emblem stamped BCM on each, has anyone seen this before ? Also the seat lug is stamps 75. There appears to various different theories on the range of numbers stamped on the Motobecane frames, I think it's safe to say it's build is around the mid 70's. I'm going to base the colour I spray on catalog pics of this period the light metallic Blue appeals with the Aluminium components to set it off.
I post more pics along the build.

Cheers guys

Velocivixen

I believe "BCM" stands for Bacoma and refers to the makers of the lugs. If you do an online search for Bacoma you will find a lot of information on them.

old's'cool

"Bacoma", not to be confused with Tacoma, producer of wood-derived products and accompanying odor, known as the "Tacoma Aroma"...
I heard tell there is also a lug manufacturer with the very similar handle Bocama...

Velocivixen

Oh cr*p. I did spell it wrong, didn't I. Yes...Pacific Northwest....Tacoma.....only one cup of coffee and ​it's very early here.

zola1

great info thank you will do

derrick

zola1

Got a question on the Huret rear dropouts here are some pics :-

mine has a bodged end stop 1st pic any idea of the correct set up ? Please see other pictures, any Huret supplier that stocks them ?


Cheers derrick

bertinjim 

zola 1-

The 73 30 and the 75 on the lugs is the angle of the tube socket and is not useful for dating production. The centre picture is correct. Huret dropout adjusters use a unique thread at 4 mm for the hole with 0.8 mm threading. Every other adjuster is 5.0 mm x 0.8 mm. However, if you can't find Huret on EBay, then the dropouts can be tapped to 5.0 x 0.8. I've not done it but Sutherlands says it is possible.

zola1

Hi thank you for the info, would these stamps indicate the year, with Huret dropouts and Bocama lugs ?

eschlwc

as far as i know, no one has cracked the code on motobecane serial numbers to indicate year or any other information. that thread i posted was established to begin a database to do so. it is far from complete.

the way we determine moto frame dates is usually relegated to referring to the online catalogs in terms of paint scheme and model options (brazing, bosses, frame material, wheel size, component groups, etc.). when found, component dates can also be helpful.

zola1

ok, i 'll try that, there are several original parts on the bike , no more blind alleys with the stamping on the frame, get on with the build..

rootboy 

Also, if I may add one caution. It can be very tricky to get an accurate measurement of the inside diameter of the seat tube using the method shown above. The slot cut into the seat lug can introduce innacuracies. Better to measure the seat post if you have it and it was a nice fit. If not, it's best to measure below the seat lug slot, which requires a different tool , or two. FWIW.

zola1

Thanks good advice, the seat post was a snug fit and I had to soak it with WD40 to get it out. The Chrome plating has corroded above he pinch point so I'll measure below that line. I have looked for any makers details, no name etc so I assume is not the original (the current seat is a modern plastic one. I'm looking at some options, Brooks look great (price !) eBay France might be worth a bit of searching. Any thoughts on the original seat post e.g was it Chrome or Alu ? Cheers

zola1

Found this link looks like it has some bits of useful date related info :-

Date of Manufacture of Bicycle Components can be used to date a bike: component dating