crank weirdness on motobecane

i have a 50v. 1977. today while riding, the pedals started pushing forward by themselves and there was some clanking sounds that seemed to be comming from the crank area. i rode in the rain all day yesterday so there is definitely some rust coloration on the chain and in the area. i also was just about out of gas when this started happening today.

i think i might lube up the chain and take it from there. any other tips?


Re: crank weirdness on motobecane


If your pedals are spinning by themselves as you ride, your freewheel is probably broken (the ratcheting mechanism that allows the pedals to drive the chain, but not vice-versa.) As for how to test it/remove it/ replace it, you'll have to await the help of someone more knowledgeable than me.

Re: crank weirdness on motobecane

i just lubed it up a little bit and took it for a rough, fast ride around my hood. no problems. the oxidation might have gummed up the works a bit.

thanks though.. and if anyone has any proventitive information to ad or thinks it's something else, please respond! thanks again.


Re: crank weirdness on motobecane

well.. the free-wheel thing is probably the most likely.. but there could be another reason.. From what i gather, this bike has a little starting clutch near the variator.

When you pedal at some minimum speed this start-clutch's pads expand outward by centrifugal force. They then contact and spin a drum that's rigidly attached to the crankshaft... then the piston moves up and down and starts the engine by pedal-power. Stop pedaling and the clutch pads retract (spring return). The engine continues to run. Whenever the engine runs that drum is always spinning.

Now if the start clutch's pads are for some reason dragging on that drum, they will force the pedals to turn.. this action is just like when starting but the forces are reversed. The engine could spin the pedals instead of the pedals turning the engine.

The cause of the pads dragging could be rusty clutch-pad pivot joints or maybe it's internal springs are weak or broken.

"THIS": moby manual lists lubricating some clutch (the variator unit?) with a grease gun / grease nipple.. as a normal maintainance procedure (Page 17). So, I'd take a look at things and lube everything that should be lubed.

Re: crank weirdness on motobecane


i think you're right. thanks for the info and the link!

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