Motobecane 1979 50v won't start

Ok to start.... I read the article about moped repair and started fiddling around with my Motobecane. I have spark, fuel moving through the fuel line, and I'm pretty sure i have compression. Now the only problem is that it won't fire, or kick over. I'll get going with the start trigger (compression release???) until it get's going and then let off, give it a little gas and choke. All the engine does is chug and when I stop moving it stops also. Is there anything that i'm missing? If anyone has any idea on what i might want to try next it would be especially helpful.


Re: Motobecane 1979 50v won't start

IF it will fire when you spray starting fluid into the air breather, then your carb is probably clogged. don-ohio

Re: Motobecane 1979 50v won't start

If it doesn't fire with starting fluid it may be timing. The Cam is just pressed on a taper . No key. After working on mine the timing was off. It a joy to retime. If you have problems checking it just send me an email and I'll tell you how I did mine.

Re: Motobecane 1979 50v won't start

Paulo Mcgovern /


Can you tell me how it is that you timed your 50 V, specifically how it it that I access the crank ( i tried a 3/8 ratched in the square hole on the right side of the engine but no go)

I do have engine experience, so I'm not a total stooge.

My nephew scarfed a 50 V out of a barn and figured that I could fix it for him. Tonight I went and cleaned the carb and checked the usual stuf. I got compression, fuel and spark so I figure it mus tbe timeing.

any advice to make me the cool uncle would be greatly appreciated.


Re: Motobecane 1979 50v won't start

First off the flywheel bolt I think is left handed. That may make a big difference. Do you have the complete manual. If not email me at with your email address and I will send it along. It shows the tools you will need to time it. I made my own and can tell you how I did it but it's a lot easier if you can see what they look like.

Basically you set the points to open 2 mm before the piston gets to top dead center. I used an old spark plug and remove all the porcelain and drilled a hole in it for a rod to slide up and down. You screw the contraption into the plug hole and turn the motor over and mark the highest point. The do it again and check to see it the points open using a ohm meter 2 mm before. Let me know if the helps or just confuses you. After you read the manual it should help.

Let me know about the manual so I can send it along.


Re: Motobecane 1979 50v won't start

Mitch Buchannon /

Is there a way to time it without a timing tool, whether homemade or not? Thanks.


Re: Motobecane 1979 50v won't start

I dont believe so. The only way with this motor is to set the cam up in relationship to the piston. The tool could be just a rod as long as you can hold it steady as you turn the crank by hand.

Re: Motobecane 1979 50v won't start

You should take your carburator apart and make sure that there isnt any rust in the float bowl. which will cause your float to stick and your moped not to run then check your main jet and lightly sand your point on your idle screw. then adjust your throttle cable and decomp cable. while its running.

Re: Motobecane 1979 50v won't start

The "required" dealer tools to set the motobecane timing are:

piston stop

timing tool(screws into the head and shows you piston position)

magneto wrench

cam puller

A piston stop can be replaced by using a strap wrench, or oil filter wrench on the flywheel.

the magneto wrench is basically a 3/8" drive. use an equivalent socket. The bolt is left hand threaded, so righty-loosey lefty-tightey.

The cam puller can be replaced with a two-arm gear puller from pep boys. i actually prefer thi to the proper tool.

The timing tool just shows you where 2mm BTDC is, so if you justs stick a thin rod, like an allen wrench for example, in the the spark hole, you can find TDC that way. Then get a tape measure and back the rod down 2mm into the cylinder. Then take the cam and replace it so two holes are at twevle and six, and the third hole is at about eleven o'clock. then tap it in with a mallet.hammer/crescent wrench/little brother/etc.

When your done, the points should open when the holes are at 12 and six.

When you bolt the magneto cover back on, make sure the holes line up with the nubs on the inside of the cover.

And that's it.

Re: Motobecane 1979 50v won't start


Excellent job of explaining how to set the timing.


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