Originally Posted by
billytwosheds
There's lots of love for French C&Vs here.
It's possible to service a cottered crank, not always necessary to replace it.
If you want to ditch the original BB/crank, Velo Orange makes a good threadless bottom bracket that will fit regardless of the threading of your BB shell. With a little math/measuring to help find the right spindle length for your application, you can open up options for replacement cranks.
Grand Cru Threadless Bottom Bracket-107mm - Bottom Brackets - Components
I have several French bikes, and they get ridden as much as any others.
I was going to suggest the velo orange threadless BB as well. I bought one in a medium length(not really small but not really long) as an "emergency" BB incase I had a bike that absolutely needed one very quickly. I figured the medium size would fit most road bikes. It may increase the Q factor a tiny bit, but it'd still be usable. (Until I had time to buy the correct BB.) Plus, having one of these around allows you to buy frames with ruined BB threads (or french/other weird BB threading) so you may be able to score a deal that would scare other people away.
In my experience, the french bikes I've worked on clean up well (mostly old Peugeots). We just make sure to keep ALL of the parts with the bike and try not to replace anything. Often times they have loose ball BBs which, if not abused, last forever. Ditto for the headset. The only thing I don't like is cottered cranks. (But honestly if it's an open ball BB you may be able to find a replacement spindle to convert it to tapered. Check your local bike coop.) You have to measure from bearing race to bearing race to get a compatible one. (Then measure for length, of course.) Unfortunately I can't comment on how well these bikes ride as they've always been too small or too large for me to ride comfortably for any length of time.