1980 Motobecane 50V

So, Craigslist is my friend (and quite probably will be my downfall). Saw the ad this morning for a 1980 Motobecane 50V, talked to the guy early evening, and by 9:00 I was headed home with a new project.

The bike is in what I would describe as "conflicted" condition. Some things look really awesome (you should see the seat on this beast! near-perfect!) and some things are in disrepair. Fortunately the (immediately apparent) things that need to be fixed are simple, like one bent pedal arm and a whole slew of broken cables/wires. The frame and fenders are in pretty good shape, just a little pitting. I don't know about spark or the carb yet, but I think compression is good just from turning over the engine by hand.

In any case, this bike will require some work. I've got a few Motobecane questions in general. Keep in mind I haven't started taking things apart yet and have only browsed through the online manuals. I just figure I'd ask for some direction as I undertake this restoration.

First, I want to make sure I know how the clutch works. When I pedal, the outside ring on the left side spins. I didn't try too hard, but I couldn't get it to engage the inner disk (figure that's attatched to the flywheel) hardly at all. I read about the decompression lever, maybe that's the secret. I don't NEED to use that on my Vespa to get it to turn over, it just makes it easier, but some of what I've read leads me to believe this is required. Is this the case, or might I need to repair the clutch?

Second, I read that many Moby models have a variator. Again, I'm comparing to the only other bike I've worked on, the Vespa, where the variator runs from engine to rear wheel. On the Motobecane, does the variator belt just run from the engine to where the pedals are, and then chain drive back to the wheel? I see a chain from wheel to pedals on the left side, but maybe I'm just hoping there's a variator in there somewhere :-)

Third, if I'm having troubles getting spark (haven't tried this yet) are there any silly wiring things that might cause problems? For example, some bikes won't spark if the taillight is out or wired wrong, etc. Lots of the wiring is messed up, so I'd like to know what basic things to check.

Fourth, if (when) I DO get this 'ped up and running, what kind of speeds can I expect? I see that there were 20, 25, and 30mph versions. How do I tell which one I have? Is there just easily-defeated restriction for the lower speed models that I can change?

Any other advice/tips/resources/wisdom specific to this kind of moped? All help is appreciated! Thanks!

Re: 1980 Motobecane 50V

Mike Scouty McScoutington /

take a look at the front plate of your bike with the vin # on it. it will tell you the speed of your bike. with a little work you can hit the mid to upper 30's on one of those beautiful bikes. you can look up on the internet/moped army site to see how the clutch works 100%. they are not too hard to rebuild if you have the tools (a good set of circlip pullers, a magnet, and a cultch puller). the decompression is very much needed to get your bike to start, especially if you have high compression. the belts on these bikes tend to wear causing them to not grab as well and that can make starting without a decomp hard. finally, you can take a look at your clutch and tell if it is a variator (it should be). one of the plates that the belt rides on will move with the belt off if you have a variated bike. it should also say on the vin plate. shoot me an email if you have any more questions about your bike.+

Re: 1980 Motobecane 50V

🇮🇹💦 Of the Loin /

That clutch on the left side is the variator. there should be a belt on there (4L320 from any hardware store) that turns it. And yes you generally need to use the decompression lever.

as far as I am aware there isnt any magic wiring setup for mobys, but the kill switch on these things is pretty useless (just use the decomp cable to kill it).

Check on that metal identification plate, the A and C models are 30MPH ones. Otherwise its determined by the carb and intake (bendy ones are the better ones)

Re: 1980 Motobecane 50V

Mike Scouty McScoutington /

some of you info is a little off mkelly. the models A, B, and C have ment differnt things over the years. in the pre 1976 bikes the A cylinder was the fastest. in '77 they changed over to the designation 20, 25, 30 mph. in 1979 they went back to the A, B, C lettering again but it was the opposite of what it was pre 76. (i am 99%sure thats the way it went, may be the opposite of that for the pre '76 and '79) motobecane bikes had 2 differnt clutchs, one was vatiated and on was not (the dimoby clutch). 4L230 is replacement belt for both om dels that works fairly well. i have found that the 17320 works a little better. it is a toothed belt which the variator calls for and it is a little thick of a belt which more closly resembles the stock belts. as far as the wiring goes if you have the proper wiring harnes for your electrical system, ie. 12V with a 12V and 6V with a 6V, you should have no problem. your bike will have the 12V system as it was made after '78. mobys have some funny electrical things with them, but it mostly boils down to flaky ground connections. if you dont have spark you will want to make sure that you have a braided non-insulated wire that runs from your engine mounts to your high coil. that grounds your frame to the engine which includes the ground for your whole ignition system. if that is good and still no spark you will see a wire that pigtails off your high coil and goes up to the front of the bike. that is your kill switch. disconnect that because they are known for going out. if you disconnect that connection your horn will still work, but as mkelly said you can use the decompression to kill the bike. hope that helps you.


Re: 1980 Motobecane 50V

Just the kind of information I was looking for! Thanks a lot!

So stopping this bike with the decompression lever is the way to go? I've heard that was a _bad_ way to do it, and it causes my Vespa to backfire. I know it works to kill the engine, but I always thought it was safer to use the electric kill switch.

"if you dont have spark you will want to make sure that you have a braided non-insulated wire that runs from your engine mounts to your high coil."

That's one of the few things I noticed electrically, and I thought it was just a sign of someone's terrible wiring job! Is the kill switch Normally Open or Normally Closed?

Miker, this 'ped looks JUST like the one in your profile picture, without the front mag wheel and with the original metal side covers. Same color, same seat (I see great potential for riding with the ladies :-D). Say, I only have one round plastic cover that goes over the magneto disk, but not one that goes over the clutch. Originally, was there a cover for both sides? I'm talking about the round ones that just cover the spinning parts of the engine, not the long ones that cover the chains and whatnot.

Thanks for offering help... I'm sure I'll need it! Now, all I need to do is make it through the day of work so I can get home to this beauty!

Re: 1980 Motobecane 50V

Mike Scouty McScoutington /

thier was not so much a cover that went over the clutch as much as a shroud. it was a metal piece that mounted to the engine and protected the belt from water and foreign objects. these bikes dont like the water so much as it breaks the friction that holds the drive belt. as far as decomp to kill its not a big deal. the reason that they say it isnt a good thing is that it can cause carbon build-up in the decomp lever. its not hard to clean out at all. i have a buddy who got a moby for $75 because it "wasnt running" and it just turned out to be a chunk of carbon in the hole. if you run a good quality 2 stroke oil you should not have a problem with carbon. last year i put about 10k miles on my bike and dont so much as have any build up anywhere.

Re: 1980 Motobecane 50V

Congrats on your Moby! You should be able to get 25-30 mph out of it..unmodified...one thing to know about is the variator needs to be greased...(the spinning part on the left?) clean out the hole and observe the brass zirk in there. It is an inverted thing...very french and wierd...they used to have a gun for it at dealers..but alas no more. I used a needle fitting with needle removed the remaining piece seemed to fit just right...it takes 2-3 pumps every 2,500-3,500 miles this lubes the variator and will make the machine last for ever! If you put in too much some will come back out of the hole...this is cool it seems to seek it's own level. Stopping with decomp lever is fine. I don't need to use mine to start but it does meake it easier. Don't know much about wiring..on your own there. RE fuel...ALWAYS mix in a sep can! 4oz to the gallon. Use high quality 2 stroke oil..ie: Castrol gtx I use premieum fuel...and a splash of stabil fuel stabilizer..some prefer sea-foam...I like stabil because of the built in measuring feature on the bottle..avail at any auto parts store. Check for rust in tank dump all old gas! Any questions just ask...many very bright people on here! Good Luck!

Re: 1980 Motobecane 50V

Oh yeah...for parts cables carbs etc try www.themopedjunkyard.com they have been very good to me! If you have carb trouble try and rebuild yours I have heard tell of a carb running sweet on one bike and being switched to another of the same model and running for crap..one of the great mysteries of our time..lol just a thought. Good luck!

Re: 1980 Motobecane 50V

I think 4 oz. of oil per gallon is too much...I prefer 50:1, which is ~2.6 oz. per gallon. I usually fill up at the gas station then pour the oil sraight in, works fine.

As for the clutch cover, it's very helpful in the rain because otherwise water gets in there and the belt won't catch, which is extremely frustrating. Also, if your pants are baggy, it's possible to get you left pant leg caught in the variator if the guard is removed!

The right side magneto cover isn't necessary. I got a cool chrome one from france though, cuz it looks stylish.

Re: 1980 Motobecane 50V

Alright... finally had a chance to look at this bike some more.

I pounded out the pedal arm that was bent before. Now it's pretty straight, but not the orignal curve it should have. It's on the right side though, so it doesn't have to clear much. It just pedals nicely now, and I didn't have to buy anything :-) The Motobecane pedals are a nice, heavy duty solid rubber.

I put a little gas in the tank and tried to pedal to see what would happen. The clutch engages, engine turns over, and the throttle works. I hear it sucking air, but unfortunately it doesn't start up.

It sounds like my Vespa when there's no spark. However, I pulled the plug out and confirmed that I'm getting a spark when I pedal... at least some of the time. The plug cap doesn't fit snugly on the plug and it looks like the part that really grips the top is broken. Where might I find a new plug cap locally? Is this something a hardware store might have?

I also suspect the carb/fuel system. I take it that it's always a good idea to clean that out on a bike that hasn't run for a while. I got 2mph when I cleaned out the carb on my already running reliably Vespa. Any tips for cleaning this carb specifically?

Compression is good by the "finger in the sparkplug hole" test.

And the best part? All the lights turn on when I pedal! No burnt bulbs, no screwy wiring...

This thing is in MUCH better shape than I expected! I expect to have it running soon, then it's a bunch of cosmetic stuff and cables.

Thanks for the suggestions so far!

Re: 1980 Motobecane 50V

Got back in the garage today. It's really cool taking apart the same parts on a VERY different machine... This is a variator model and the way they do the variator is pretty sweet. The whole engine is on a spring-loaded pivot to maintain tension because it only has 1 variator pulley.

Replaced the spark plug. The Motobecane and my Vespa Bravo use the same plug, so I had a spare lying around. Lucky me!

Cleaned out the carb, no problems there except it was a little stubborn coming off. Cleaned and cleaned grease of the engine and inside the frame. It's looking a lot better!

When I pulled the gas hose off the carb I noticed that there wasn't even a drop coming out of it. That was strange, so I played with the petcock for a while (that doesn't sound right... :-P). There was a little gas in the tank but no matter which way I turned the lever, none would come out. So I went to remove the petcock from the gas tank, and instead of unscrewing nicely, I managed to snap it off right at the threaded part. And then all the gas that was in the tank came pouring out. Hooray.

I'm currently attempting to bond the petcock back together with some JB Weld at least temporarily, but that spells l-e-a-k-y even if it works. I'll definitely need a new one. Oh well, it's hard to take something apart without breaking at least ONE piece of it, right?

Okay, enough bad/boring news. There is also some fantastic news: It runs! I think last night it was just a lack of gas due to the faulty petcock that caused it not to start. Tonight, I didn't really have a gas tank to work with, so I just poured (and spilled a lot) some gas into the carb via a spare piece of hosing. Hardly any made it in, but enough to start the engine and buzz me down (but not back up... and it's a big hill) the driveway. This thing zips! For not being warmed up and not having been run in ages, it was very responsive and fast.

And to think, all I need is a damn petcock! Then I can go cruising before I unload this monster.

Also, the horn is nice and loud, the lights work perfectly (had to replace the taillight bulb... one filament was dead) and the body is actually in pretty great shape. I got a better deal than I thought at the time!

Re: 1980 Motobecane 50V

Mike Scouty McScoutington /

does this beast have the side panels? they really dress it up.

Re: 1980 Motobecane 50V

Side panels - oh yeah. And they look pretty good, too. One has a big gash from where the best pedal hit it, but the rest of the paint is fine. I really like the paint on this bike; it's almost sparkly when you get it shined up.

In other news, the petcock repair didn't work (no suprise). However, I've found a temporary workaround by threading a large rubber gas line into the gas tank where the petcock was. I wouldn't go more than a mile away from home like this, but it works and doesn't appear to be leaking. Of course, if it comes loose, the whole tank empties, and then I'm screwed wherever I am. I'll order a new petcock tonight :-)

So I was finally able to get it going a little bit and this thing is a rocket compared to my Vespa. By feel alone I'm sure this is the 30mph version. It's also the C model, so I think what you were saying is right. It zips right up the hills, too, whether that's the variator or just raw power.

Too bad I'm gonna sell it :-) Then I'll be able to make my Vespa into a serious monster.

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