calling motobecane enthusiasts...

I have the engine removed but the clutch with the pully wheel spin freely. Maybe Im missing something. I would think that i need this pully to be fixed to the engine crank so that I could pedal and the belt would turn the engine over and start the engine. But is that correct?

When i the engine was still attatched to the bike, I tried pedaling it to start the engine and the pully would just spin without the motor. Therefore making it impossible to start the motor.

So if anyone could explain what is going on here I would be greatful.



Re: calling motobecane enthusiasts...

Switch it from "M" to "V" little switch, usually a bitch to turn. on the big pulley with the pedal arms

Re: calling motobecane enthusiasts...

The outside part turns free till the RPM's increase then the clutch grabbs it and sends the power to the rear wheel.

The outside center is connected to the engine.


Re: calling motobecane enthusiasts...

I hate that little switch!

Someone said when you get it in the correct position "Leave it there"


Re: calling motobecane enthusiasts...

Thats not the problem. I have the switch turned to motor, but the pully ON THE MOTOR just spinns FREELY of the motors crank when you pedal. If the motors crank isn't turning, its not going to start.

Re: calling motobecane enthusiasts...

I know how the clutch gets power to the rear wheel. How about getting power from the pedal pully to the engine pully so the engine will turn? It engine pully is just spinning free of the engines crank right now...

Re: calling motobecane enthusiasts...

We can only assume you know nothing about the engine operation or that others will know nothing, so we try to cover all the relevant information.

Is your clutch stuck or broken or both?

The pedals turn the large pulley and the belt turns the small pulley but the clutch never grabs and spins the engine.

Is that the correct order of things?

Can your engine be turned by hand?

You may need to replace or rebuild your variator.


Re: calling motobecane enthusiasts...

Midlife Crisis Alan /

Make sure your decompression switch is fully opening - my engine will not kick over without it fully depressed. Just a thought.

Re: calling motobecane enthusiasts...

Seth, have you tried rolling down a hill on the bike, or are you just trying to kick it over on the stand? It sounds like maybe you're just not spinning the clutch fast enough to get it started, or the decompressor isn't working as Squid-A suggests. If the flywheel doesn't start spinning when you roll down a hill, and you're sure your decompressor is operating, then I'd say your starter clutch is worn out.

As for everyone else and their complaints with the driven pulley switch: I use that switch every day (I ride to the edge of campus, then pedal to the bike racks) and I have no problems with it. If it doesn't engage right when you first try, just back off on the switch a little, roll the rear tire backwards slightly, and try again. Once you know how the switch should feel when it engages successfully, it's easy.

Re: calling motobecane enthusiasts...

What my guess has been is that there is a clutch problem or a variator problem, but ive never woprked on a motobecane so Im not sure how they are supposed to work.

I know how an engine works quite fine so dont worry about that. I think i know how the engine starts... That is, you put the switch to motor which drives the pulleys, which turns the engine over. And my problem is the pulley on the engine just spins and spins and spins around the engines crank. Its not turning the engine over.

To understand the problem, eliminate the bike. On the crank shaft of the engine, there is a pulley. This pulley is used both to turn the engine over when starting (by pedaling), and it provides the power for the belt which would drive the rear wheel. The problem is, this pulley is spinning FREE of the engine crank. If im not mistaken, it should be LOCKED to the engines crank. Because if it spins freely, separate of the engines crank, you cannot put power into the engines crank and turn the motor over to start it.

And it's not the belt slipping.

I think I've made it as simple as I can.

It's not the decompressor... This has as much to do with the decompressor as the color of the bike...

Thanks for your guys knowledge and help!

Re: calling motobecane enthusiasts...

" The problem is, this pulley is spinning FREE of the engine crank. If im not mistaken, it should be LOCKED to the engines crank. Because if it spins freely, separate of the engines crank, you cannot put power into the engines crank and turn the motor over to start it."

When you say the pully (variator) on the engine is spinning "freely", is the clutch (on the outside of the variator) also spinning? If the clutch is spinning, does the whole thing spin when you pedal hard or just the outter rim.

If just the outter rim the cluctch is broken.

If the clutch is not spinning the pins that connect the variator to the cluctch may be missing or broken (odd).

Also is your magneto cover on the other side of the engine spinning at all?

If the magneto is not spinning the bike will never start and your clutch or connection between the variator and cluctch is broken.

If the magneto is spinning the bike may have other issues:

typical moby starting probs:

loose/worn belt

cracked mounts

decompressor not open fully

everything else in fred's guide

Someone with more knowledge correct me if im wrong, i'm unclear as to whats really going on with his bike.

Re: calling motobecane enthusiasts...

"When you say the pully (variator) on the engine is spinning

Re: calling motobecane enthusiasts...

sounds like a bad clutch. It must not be enguaging. Probably best to open it up (think you need a special tool) and check things out or strait up replace it.

good luck


Re: calling motobecane enthusiasts...

I don't ever use decomp lever when starting my 50v always lights right up....the damn lever in question howenver is a bitch! at least on my machine mine is jammed between pedal and engine rolling back has NO effect! Howenver big rides and starks easily...WTF?!?

Re: calling motobecane enthusiasts...

Mike Scouty McScoutington /

my money would be on a bad belt. i cant tell you the number of times i had a belt strech out on me and make me look like a fool cuz i have to run with my bike for 4 blocks before it kicks over. i never try to pedal start my bike. you can move it faster if you bump start it. replacement belt size: 4L320, or 17320. you can get them at an auto parts store.

Re: calling motobecane enthusiasts...

You have your levers mixed up keller_stephen.

the decomp lever is on the right handle bar. use it to start and stop the engine.

You are right that the Bike/moped lever on the pulleywheel is shit, that should be left in the moped mode always.

go for the 17320 belt over the 4l320. it just lasts longer

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