Motobecane doesn't appear to have built any coding into their serial numbers. They appear to be purely sequential. I've collected about a handful of Team Champion serial number and with the exception of one, they all seem to fit the standard Motobecane format. Based on the features and what I've collected, I've have expected the OP's bicycle to have a serial number in the mid 4xxxxxx range.

@architect215 - a bit late as you are near 10 posts but you can add pictures to your gallery in your profile. Others can then post here.

@SJX426 - thanks for the hint. album uploaded!

Link to OP's photd albums https://www.bikeforums.net/g/user/529264

The rear derailleur has a 1980 date code, while the crankarm has a 1981 date code, so it should be a 1981 model year, as the 1982 model year had a chrome plated rear triangle.

Great to see the additional pix, a really fine bike! So did we learn what size seat POST this takes, to determine if the (presumed now) Columbus tubing includes SP for the seat TUBE? Cinelli BB shell as the catalog spec noted in '79, but yes this date estimate makes more sense given the portacatena Campy DOs.

Thanks to everyone for their time and expertise! I've logged nearly 200 miles on it since my purchase back in November. I guess it's time to put it away for the winter now and wait for warmer and drier roads.

I can’t speak for the OP’s bike, but my 1978 (SL frame, 54cm) takes a 26.6 post.

I measured 26.68 with my vernier calipers

got my 10 posts in, so here's some more pics (same as in my personal album).

Another interesting detail is that this Cinelli "SC" investment-cast BB shell has "FRANCE" in the casting. I don't think this refers to country of origin (AFAIK there was never any manufacturing of Cinelli parts outside of the greater Milan region, tho they certainly farmed out production to many contractors). Rather it must mean sized for metric tubing and with FR threading. I think this may not be the first time this detail has come up but the last time was long enough ago so it all seems brand new to me, now!

Hi guys. I just picked up that same bike.