Motobecane Conversion

As mentioned in my last post, I've started working on a 650B conversion on an old Motobecane. I picked up the frame pretty cheap - the paint was tired, but the frame seemed to be in good shape structurally, seemed to have good wheel/tire clearance, and I thought it might make a good candidate for such a project.

The model is the Grand Jubile, which was one of the better-quality models from the brand. In the early '70s the model was built with Reynolds 531 tubing and came equipped with Huret Jubilee derailleurs (hence the model name, I suppose) while another model, the Grand Record, came with Campagnolo Nuovo Record derailleurs (again - reflected in the name?). Above those in the company lineup were the "Le Champion" and "Team Champion" models. I did some research into the frame to figure out when my particular bike was made and how it might have been equipped originally. Big clues came from the frame tubing - Vitus 172 - and the rear dropouts, which were marked "SunTour." Those details meant that this bike would have been from 1977 - the first year for that switch in tubing choice, and by which time it would have been switched from the French Huret Jubilee derailleurs to SunTour. The Vitus tubing doesn't have quite the same cache as the Reynolds, but the quality is still quite good.

There are the catalog pages from 1977. As you can see, the Grand Jubile was available in "gunmetal gray," or in the "flam red" like mine. (scans from bulgier.net)

The paint on my example was really dull and oxidized. There are also a lot of chips and scratches. I was able to do something about the oxidation by using some polishing products from Meguiars. This is what it looks like after the first two steps - a definite improvement. I may take some time to touch up the worst of the chips and scratches if I can find a good match.

I've used these "Mirror Glaze" products from Meguiars on a few vintage bikes with great results. Start with #1 medium cut cleaner, followed by the #2 fine cut cleaner - and the shine really starts to come back. Finish up with the #7 glaze - and then top it off with wax.

I like these lugs - they have a cool shape to them, but I find them a little puzzling. The catalog says they are Nervex Professional, but there are some notable differences between these and the Nervex Professional lugs I'm familiar with, and I haven't been able to find any exact match from any of their old catalogs. All I know for certain is that they were used on a few different Motobecane models for several years through the 1970s.

This is the Nervex Professional lug shape that I'm familiar with - the ones on the Motobecane have some similarities - but many differences as well.

The headset here is a French-threaded model from Velo Orange. It's mostly aluminum, but with steel races, and the quality is much nicer than what this frame originally came with. However, getting it installed took some time and effort. I was able to remove the original parts easily enough, and the new cups and races pressed into the head tube without much trouble. The trouble came with the fork crown race. I gave it a good try with my crown race setter but it simply would not go on. I took the race off and measured it with my digital calipers - 26.4 mm (just as marked). I measured the crown race seat - 27 mm (actually, it varied slightly depending on where exactly I took the measurements - from about 26.8 to 27.1). I looked up "French headsets" on Sheldon Brown's website and found this: "Headset crown race: 26.5 mm (sometimes 27 mm)". Great. I don't have a crown race cutter. I spent some time with a small file and carefully got the crown seat to 26.5 - and sanded a little off the inside of the race. A bit of grease and a couple light taps with my race setter and we were good.

There's the seat lug - and a badly damaged Vitus tubing sticker. There's also an ugly and delaminating sticker from the bike shop that I assume sold the bike originally. I can't read the name of the shop, but it appears that they were also a Raleigh dealer (I can just make out that much of it) and they were in Tacoma, Washington. I'll have to work at it to see if I can get that off.

Here's that shop decal - in process of being removed bit-by-bit.  I eventually got it all off, and used some "Goo Gone" to remove the leftover adhesive. I'm not going to worry about the tubing sticker - though reproductions are available.

The next step will be to install the bottom bracket and then the crank. For the crank, I got a nice Velo-Orange crank that someone must have used a short time then removed for whatever reason. It had a couple of minor scuffs or scratches, but it was also just a fraction of the price of a new one (they currently run about $200).

In terms of style, the VO crank doesn't look significantly different from what would have been there originally. The gearing is a very useable 48/34. I've got a couple old pairs of pedals to choose from, but haven't decided which ones to use.

That's all for now. My next update will look at modifying a current model stem to work with a vintage French bike. Another fun challenge. To be continued. . .