auchencrow

I've been working a little on this c.72 Motobecane. (As you may recall from my prior thread, I bought it to flip, but the Devil is making keep it, at least for now.)

I have a lot more work to do on this bike. So far I've cleaned up the frame, and to inhibit rust, I clear-coated a couple big paint scrapes on the right chainstay and underside of the bb shell with some clear nail polish.

(Predictably, I could not find red-metallic-translucent-lacquer in a spray can at Lowes, and IMO, clear is better than mismatched paint.)

The fork needed painting too, because it was a chromed replacement for the original item. The huge expanse of chrome did not look good on this bike, so I decided to rattle-can it gloss black instead.

I was thinking of black plastic fenders for it, but for now, I just ordered some black Tressostar tape and brown hoods.




Next, I noted that the Stronglight crank is marked 9/16-20.





- This led me to believe that the crank was originally tapped to 9/16-20 for the US market, but oddly, I find that only the old (original?) West-German made chromed steel pedals will thread-in by hand: They are marked "FR" on the quills.

-If this means they are French, than why do the cranks say otherwise?
I was considering some new pedals, but I don't want to force it.

I need some guidance:
Is it safe to tap these cranks to 9/16 x 20?
And how can a crank that was supposedly tapped to 9/16-20 revert to a French thread?


PS- does anyone know how to extract a drop-out stop-screw that is broken off inside?

Road Fan

I think it's probably French-made, but why wouldn't a French company starting to compete with the rest of the world start to broaden its technical standards?

Not sure if Moto off-shored it's frame fab in the late '70s.

noglider 

I'd bet money that it's French made. I've never heard of a Motobecane-owned factory that was outside France.

The French did start sending us bikes with English threaded pedals in the 70's before they English-ified the diameters and threads on their frames. The latter action took place in the 80's. I think the freewheels came in English thread around the same time as the pedals did, but it might have been a little later, too.

You'll probably need an easy-out to get that screw out. And a mighty small one, at that.

It should be safe to chase the threads of the cranks with English thread taps, but you wouldn't be changing anything. Why do you want to do this? You may have French-threaded pedals, if they're going in too easily. Rather than labeled L and R, they might be labeled G and D. If they are, put them aside for a rainy day, and don't use them on this bike.

noglider 

And what is it with wrenching outside? I notice a lot of folks take pictures like that. Isn't it extra trouble to move all your tools out?

jmichaeldesign

French Thread and Standard thread pedals are very close to the same. A french pedal will fit just barely loose in a standard crank. A standard pedal can be threaded into a french crank if enough force is applied. Many people will choose to put standard pedals in french cranks without re-tapping. The pedals will often actually tap the cranks just slightly.

From Sheldon

"Most French bikes sold in the U.S. used standard thread pedals:But older bikes made for the French market used a slightly smaller thread:If your cranks are made for standard-thread pedals, a French-thread pedals will fit in, but be very loose and will be unusable. It is not possible to put a standard pedal into a French crank without considerable violence."

I would disagree that you need "considerable violence" to put standard pedals in a french crank, its tight enough that you know its not the best idea though.

JohnDThompson 

The cranks are already 9/16 x 20tpi; the stamping is original from Stronglight. Motobecane was one of the first French companies to start spec-ing outside of French standards. Regarding reverting to French thread pedals -- these are so close to each other as to be interchangeable in many cases -- TA even made pedals between the two standards. A French thread pedal may be a little loose in an English thread arm -- crank it down and see if it wiggles.

Use a knife and needle-nose pliers to dig out that black plastic piece at the end of the slot. Once that's out of the way you shoulkd be able to grab the bolt and unscrew it. Use some penetrating oil to help things along.

auchencrow

Hi Tom -
The W German pedals that are installed now were quite rusty - I treated then with OA and oiled them with light oil subsequently. They look pretty good for now, but I don't know how long they'll last. (Oil is not a good rust inhibitor in the long term.) Also, the dust caps are swedged in so I can't rebuild them.

The cranks are not what they say they are - or certainly they would accept a standard 9/16 pedal.
If they are French, it's manageable - My concern is that if they are "some other" slightly different pitch, I could end up with a looser-than-English threaded crank.

-Just a few more steps than it would be if my stand was inside my garage. On nice days I tend to make that small concession. It helps than my stand is quite portable.

auchencrow

Thanks John - Your input about the French and English threads being so darn close is good input to me: The W German pedal that screws in, and my 9/16 pedal that doesn't, LOOK identical. I have a hunch that the cranks were intended to be 9/16, but are likely French, in which case I should be able to tap them out.

This is an older Moto (guessing '72 or so) and the crank could be a transitional piece for Stronglight. - One that missed the secondary tapping operation at the factory.
A real possibility I would think, if they were still serving French threads to other customers at the time.

auchencrow

Thanks JMichaeldesign - As always Sheldon had the detail to the third decimal place. I did not try to force it so I don't know how "considerable" the violence would be, but I tend to be a little conservative whenever it comes to removing metal.

Grand Bois

Thats why it's so easy to tap French pedal threads to 9/16". Very little material is removed.

old's'cool

Are you kidding? The nice weather season is too damn short, most places, to spend your weekends as well as weekdays cooped up indoors.
I've been putting off all my urgent indoor home improvement projects in favor of non-urgent bike projects that I can do outdoors, while the good weather lasts. I guess I'm just an outdoor person.

Heck, right now I'm sitting outside on my deck in shorts listening to crickets while I type.

unworthy1

BTW, Sutherlands says that the Huret DO takes a 3M x 0.6mm screw, that's the unusual coarse thread for 3mm fasteners, the finer 0.5 is far more common. Don't know how important that may be in the soft-ish black plastic slug, but just so's ya know.

Collin2424

This makes perfect sense. My Motobecane Le Champion had English-threaded pedals installed that completely stripped the crank arms. It originally came with French-threaded Lyotards. So, the person before me obviously thought they were close enough to try "regular" pedals. Doh! Thanks for the insight

-Collin-

auchencrow

Oy vey!
Here I was thinking it would be difficult enough to find M3-0.5 x35 dropout adjuster screws, springs and cap nuts. At that I guess I'll see how it goes with the left side. I know I can fabricate a half moon spacer to serve the purpose if need be.

Thanks for the warning, unworthy1. It's good to know before I start removing what's there.

Bikedued

I would date that bike to mid seventies at the least? The paint scheme and Jubilee derailleurs. I'm not sure when they started making those shifters, but they're on my 78 Grand Touring. Didn't Moto's have Swiss bottom brackets during that time period?,,,,BD

noglider 

I agree and estimate 1976. I paid a lot of attention to bikes then.

I don't know what years they used Swiss threads in BB's, but this bike probably has them.

auchencrow

Hi BD !

The power shifters are unoriginal because I didn't like the barcons, but you may be correct about the time-frame:

Except for Weinmann brakes (which had added quick releases by '74) and the old pedals (which had gone to 9/16 Atoms by '74) the specs closely match the '74 catalog.
The paint scheme is the same as my '74 Moto GT, but may have been used earlier.
Also, by 76 the GJ went to Japanese components (SR Cranks etc) so my bike could be earlier, but not much later.

auchencrow

Hi Tom -
I very much doubt that it has a Swiss BB - I did not unscrew the fixed cup to verify it, but according to Sheldon, Moto introduced Swiss threading late in the 70's into the 80's.

auchencrow

BTW here are the pages from the 74 catlog - the earliest I found online.






BTW - The wheels on both my Grand Touring and this GJ are later (clincher) Weinmann -Normandy replacements.

JohnDThompson 

Just leave them out if you can't find replacements.

Grand Bois

At least you didn't waste your money on screws that don't fit like I did.

noglider 

I stand corrected on the year and the BB threading.

kroozer 

It's either a 74 or 75, they were identical as far as I can tell. I have one just like it and have always used Engllish-threaded pedals with no problem. I believe the BB is French-threaded, but I haven't been able to remove the fixed cup so can't say for sure.

old's'cool

My '78 has Swiss BB threads.