Motobecane Top Speed problems

I have a 78 Motobecane 50V, and it won't get over 15mph. The carb is spotless.

Also, if I give it a tiny bit of choke by barely depressing the lever, I can sometimes get a little extra speed (up to 19-20mph) out of it. Since the choke restricts airflow, that make me think its running too lean, but other than what I've already done.

Is it possible the throttle cable isn't adjusted right and I'm never getting wide open?

Below is the list of things I've done to it. Any ideas on what else to check?

- Replaced petcock and fuel line

- New spark plug

- Cleaned exhaust port on engine



The Passion of the Moby

Ah I have a bunch of mobies, they drive me crazy.

-Make sure the carb is pushed ALL the way onto the intake valve, and make sure the little rubber bushing is in there.

-Did you make absolute certain the jet is CLEEEN? Does carb cleaner shoot through it like a squirt gun?

-Mobies have a completely movable cam, which means it is completely easy to mess up your timing. and you need a special puller (mopedwarehouse) to get at it.

-Get the puller, and clean your points, set gap to .12 -.14

still not running well?

-flywheel cap is reverse thread. use puller to loosen cam

-to set the timing on the moby you can use the cigarette paper method. although you will need an asistant.

-remove the spark plug, stick an allen wrench down the hole, and rotate the engine slowly, you want the points to begin to open when the piston is 2mm before TDC (the top)

-stick the cig paper between the points, and have your assistant pull on it slightly (not enough to pull it free)

-get out a ruler with mm, break it, and stick a piece of it between the cylinders heatsink, pointing up next to the spark plug hole.

-as you rotate the engine, the allenwrench should ride up and down next to the ruller,rotate the cam untill the paper comes free at the right time,2mm TDC

-tap it tight with a pipe when you are done, then check it again.

and download this

Re: The Passion of the Moby

David Dear /

I will check the carb attachment and the jet. I also have a new rubber bushing that i'll replace while I'm at it.

Would bad timing cause the symptoms I've described? It runs evenly and consistently up to 14mph, it starts on a dime, it revs while on its stand with no irregularity, etc.

How do you know if the throttle cable is tight enough? I've adjusted to the max with the adjustment nut, but I'm thinking I could loosen and pull the cable through further.. Thoughts?

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