Back in 2015 I managed to pick up a couple of these Motobecane motorcycles. One ran for all of 15 minutes until the case seals disintegrated. The other was seized from sitting; but after freeing up the pistons and reeds, it actually ran (sort of) for a few months. I sold the running bike to someone in LA when I decided I had to have a Dodge Rampage. Later, after a year or two, I decided to buy it back -- at this point it wasn't running anymore.
In the intervening 2-3 years I struggled to figure out how to get it running right. Jesse has one, but has also struggled to get his going reliably. There are one or two others, in the Midwest I think, but I'm not sure if they run either. Finally this summer I managed to figure it out, and to celebrate, and maybe help someone else out with theirs, I thought I'd post about it here.
So, there are two bikes, one from a storage unit in Spokane, WA
and one from an original member of the Mosquito Fleet
Both came with a 16 mm Gurtner variation that looks a lot like a Dellorto SHA
I became so frustrated trying to get these running, that I just started working my way through all the various issues so I could focus on the ignition timing.