Motobecane D52 5 speed gearbox rebuild

Published on 12 September 2023 at 19:48
Motobecabne d52 gearbox internals
motobecane d52 gearbox casings put together

The two halves of the gearbox back together -- they didn't stay this way for long.

Motobecane d52 5 speed gearbox with sprocket fitted

The sprocket is now fitted, the box is running freely.

e d52  5 speed gearbox selector mechanism

The selector mechanism back in place, it tested fine, everything was working splendidly except for the kick start mechanism, so it all had to come to bits again.

Some things are just really difficult to do. Plaiting fog is one, knitting dry spaghetti is another but the thing that beats everything hands down in the difficulty stakes is rebuilding a Motobecane 5 speed gearbox. It is, what my Father would have called, an absolute bastard of a job, one that I do not wish to repeat. I will say that life was made much more difficult by a distinct lack of light and my complete failure to keep my workshop clean and tidy but blimey, it's a right old nightmare.


The first thing that produced Olympic standard swearing was the detent balls that give the gear change a good firm click and stop the bike from jumping out of gear. There are 4 4mm balls and 4 x 4mm od springs that are retained by the inner race of the shaft bearing. Trying to get all 4 compressed and the bearing over them is an absolute nightmare. I spent far too much time trying to find springs that had shot across the workshop. I had a good supply of 4mm ball bearings but no springs in that size. I did get them all present and correct once but I then found when the box was altogether the kick start mechanism didn't work so I had to take the box back apart. It was when I did this that I lost 1 of the springs and at this point have been unable to find it. I have ordered some new ones, I guess I now have to wait for them to arrive.



The next thing that would have taught any passing Nuns a whole new style of vocabulary was the gear shift shaft, it is a real pain to manipulate it while guiding the two halves of the box together. It's not impossible but it is difficult, I wanted to heat one half of the casing to make it seat over the bearings more easily, that meant I was then handling hot metal so it made it easier in one respect and harder in another.

I managed to get the box al together and tested all the gears, great it was working really nicely. It was a wee bit tight at first but a few taps with a small hammer helped settle things and it was working perfectly, it felt good and sounded fine, even though there was no oil in it at the time.

The destruction of my mental health became total when I went to test the kickstart mechanism -- you guessed it, it didn't work. There was no option but to take the box back apart, this was when the nastiness with the tiny springs happened. I found what the problem with the kick start was, I was furious with myself for not spotting it earlier, I should have noticed a cock eyed washer that was stuck on the helical drive, it was stopping the two ratchet wheels from engaging with each other so the kick start shaft just rotated without doing anything.

oh well, at least I now know all the bearings and seals are correct, that the gearbox will work and that the kick start will work too next time I put it back together.

I hate the fact that it is now well over a week since I took it apart and I am not sure of a few of the details concerning which bolts went where, of course I took photos, of course they no longer seem to be on my camera card. It will all become obvious as I start to put it back together I suppose.

Then, as if matters couldn't get any worse I got a letter from the DVLA saying the proof of age I sent for my Bianchi Stelvio was not acceptable and my request for registration was rejected. I would have thought the information sheet that came from the museum and the catalogue entry from Bonhams would have been enough, but apparently unless I can prove the age of the bike I can't register it. You have to get a recognised club to create a dating certificate but given that Bianchi ceased to produce motorcycles donkey's years ago and that they were in Italy and very few records exist I don't know how this is going to end up, it is incredibly frustrating, I need beer.

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