wisper chain

[theskip1]

i have just aquired a second hand wisper works 905 se sport and have noticed that when in super low 1st or 2nd gear and i back peddle the chain gets thrown. at first sight it does not seem to be something that is easily rectified. is this a design flaw or is there some fix that can be done ?
tk.

 

[flecc]

This is not unusual with derailleur gears, it's best to avoid sudden back pedals.

It occurs because back pedalling means the chainwheel pulls on the rear mechanism, so the slack that appears in the chain then allows the chain to "snake" and jump.

Things that make it bad:

A freewheel/cassette that's binding, make sure it spins backwards freely. If there's a plastic spoke protector guard disc behind the sprockets, that often causes binding. Remove it.

A binding chain link, make sure that every link around the chain is free to pivot freely on the next link.

A bent chainwheel, check it by rotation for trueness.

The upper run of the chain touching the frame or an obstruction when the top run goes slack though back pedalling, causing the chain to snatch.

Too long a chain, shorten.

Heavily worn chain or sprockets, especially "hooked" sprocket teeth.

Rear mechanism spring tension inadequate, get dealer attention.

 

[theskip1]

This is not unusual with derailleur gears, it's best to avoid sudden back pedals.

It occurs because back pedalling means the chainwheel pulls on the rear mechanism, so the slack that appears in the chain then allows the chain to "snake" and jump.

Things that make it bad:

A freewheel/cassette that's binding, make sure it spins backwards freely. If there's a plastic spoke protector guard disc behind the sprockets, that often causes binding. Remove it.

A binding chain link, make sure that every link around the chain is free to pivot freely on the next link.

A bent chainwheel, check it by rotation for trueness.

The upper run of the chain touching the frame or an obstruction when the top run goes slack though back pedalling, causing the chain to snatch.

Too long a chain, shorten.

Heavily worn chain or sprockets, especially "hooked" sprocket teeth.

Rear mechanism spring tension inadequate, get dealer attention.

yes i have checked the usual reasons but this just dosn't seem to line up. i think i might take a link out as it does seem a little slack.