Replacing motobecane chain

Motobecane Rookie /

Hi all,

Have two questions on this, hoping I can get some help. I am replacing the main chain on my moped, the one that (i think) connects to the pulley and to the engine.

-what's the best way to go about doing this? Do i need to both remove the pulley and loosen the back tire to get the chain on, or just one of these?

-how do i (cut) the chain to the right size?

-how do i know how tight the chain should be? The reason I'm replacing the chain is because the last one snapped, I think because I had the chain on too tight.

if anybody knows any videos or useful links that can help, that would be helpful. I can also send pictures of the moped if that helps as well, its a 1979 motobecane 50v moped.


Re: Replacing motobecane chain

When you are sitting on the bike there should be about 3/4 inch play in the chain. (edited)

Re: Replacing motobecane chain

There is not a chain that connects your pulley to your engine. Your main chain connects your pulley to your rear wheel. To install the new chain, put it on your bike and see how many extra links you have with the tire in the closest/mid position. You only need to loosen your rear tire and tensioners to install the chain. You want the chain to be tight, but loose enough to pinch a 1/2 inch.

Re: Replacing motobecane chain

Motobecane Rookie /

Hey thanks for the help, can I ask one more question?

I've learned how to remove links from the chain and think I have a good sense of how long it needs to be. However, I am still not certain of how I should be loosening the tire, or what the tensioners are. Attached photos of the rear tire.

To loosen the rear tire, should I be loosening the six bolts keeping the sprocket onto the bike? They seem like a pain to remove with a normal wrench. Or do I just have to loosen the main bolt in the middle (the one connecting to the orange bar?) This doesn't seem as if it would give the back tire enough wiggle room.

Thanks again.


Re: Replacing motobecane chain

You need to loosen the main bolt in the middle connected to the orange bar. Tensioners are the screw looking things that are at an angle below the bottom of the shock. When you tighten those, it will push out the main nut you loosened and create tension on your chain and give you more of a precise and reliable fit. (edited)

Re: Replacing motobecane chain


It should be 1/2 to 3/4 inch free play. Which means it should only move 1/2 up or down from its resting point.

Re: Replacing motobecane chain

Throw on your new drive chain onto the sprockets.

Back off the tensioners completely.

Loosen the axle nuts so that you can move the wheel nut still enough resistance so the nuts will hold the wheel in position on the trailing arms.

Work on the left side of the bike and pull the wheel back so that there is 1/2 inch total travel of chain slack measured half way between the front sprocket and rear sprocket.

Adjust the tensioner on the left side so that it just touched the axle nut on the left side.

Move the wheel sideways at the rim so that the tire is centered between the two trailing arms.

Adjust the right side tensioner so that it just touches the axle nut on the right side with the wheel centered.

Tighten up your axle nuts.

Sit on your bike and ensure there still is slight slack on your chain. If you are a hefty person or your shocks are weak you may need to repeat the process with a bit more slack in the chain than 1/2 inch total.


Re: Replacing motobecane chain

Bruce Zapper /

After reading this man do I feel smart! A chain seriously!

Re: Replacing motobecane chain

Bruce Zapper /

I need help I let the air out of my tire how do you get it back in?

Re: Replacing motobecane chain

When you are new, how else would you learn but to ask? Not everyone grew up with these things, or has a natural aptitude for mechanics.

Re: Replacing motobecane chain

Bruce Zapper /


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