Ehrlich Motobecane First look

Published on 29 August 2023 at 18:46

With the remarkable little 50cc engine having been left to soak in penetrating oil for 15 hours it was time to see if my miracle cure had worked it's magic. It had, it turned over much more easily than I thought, although it was apparent the magneto magnets were rubbing on the coils and causing some binding. I wasn't too bothered at this stage, I was just happy that it wasn't irreversibly seized and that it was likely to be recoverable. It even seemed to have some compression - not much but again enough to give me hope. I noticed that it has 2 head gaskets fitted so maybe the compression is quite low anyway.

I adjusted the coils a bit so they didn't rub any more and span the engine, it actually feels pretty good, I think the bearings may be ok. It's no big deal if not, they are only about a fiver a piece - standard SFK stock items.

Next job was to see if I could get a spark, there was an ignition coil in the box of parts so I just had to join that up to the wire that came out of the small coil in the ignition plate. Before giving it a whirl I cleaned the points and checked them with a meter, I checked a few other resistances while I was in there. I was getting a dead short down to earth - not good, I thought perhaps the condenser was shot but then I spotted the problem - one of the tabs that goes to the points terminal was shorting to earth - very simple fix.

I took the plug out and connected it it to the coil's HT lead, gave the engine a spins and was rewarded with a lovely healthy blue spark.

So, I now have an engine that turns, an ignition system that sparks, some compression, I think this thing is going to run.

My joy was short lived when I turned my attention to the gearbox - here the news was not so good. The bike runs the standard Motobecane 5 speed gearbox, it is a separate unit driven by a vee belt. The clutch is an external air cooled unit - a very simple single plate affair which is worn but should be ok. The seller had warned me that the clutch push rod was missing, this turned out to not be the case, it was present and was doing what it was designed to do so that was one positive. The negative was that the kick start shaft was seized, the output shaft was seized and the gear selector was selecting nothing. I filled the box with oil and gently warmed it, which helped a bit but it was fairly obvious that the thing was not healthy. I consulted the manual but could not get my head around how it hung together, there was nothing for it, I had to start taking things to pieces. As soon as I got the selector cover off it became obvious how it worked, it also became obvious that there is a good chance it will never work again. It is very, very rusty in there, the oil that I had put in now looked like a massala gravy - all sort of brown with lumpy bits in it. the selector mechanism is probably reusable, the bearings are all standard SKF's again so that's no problem but my big fear is that the gear shafts and clusters will be beyond use. I will need to strip the box all the way before I know for sure but I do know for sure that at the moment the gears that should slide along the shaft don't.

motobecane 5 speed gearbox with sselector cover removed
motobecane 5 speed gearbox selector cover
motobecane 5 speed gear box selector mechanism

Next job is to remove the selector assembly as a single unit and have a better look, I think it's probably ok but the siezed up shaft is stopping it from selecting any gears. A complete strip and rebuild is required in any case as the bearings are definitely shot.

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