Sun Run 24T stiff

[John_rodbard]

Hi

Can anyone help me out, my youngest son has a mountain bike with a Sun Run 24T front derailleur, it is incredibly stiff, does anyone know why this is, to change up is really hard, changing down sweet as a nut!!
Any ideas please

Thanks

 

[steve50]

Inner cable damaged perhaps.

 

[themosquitoking]

Changing to a larger cog is always harder than changing to a smaller one as tension has to be increased rather than released.

 

[mrandmrspoves]

I don't think this is a cable problem as that would normally cause problems changing onto the smaller chainring. (Changing up happens with the cable being pulled by the lever, whereas changing down happens under pressure of the return spring in the derailleur)
If the cable has been replaced recently it might not be clamped correctly, it could also be that the High limit screw needs loosening (turning anti-clockwise) Other possibilities could be that the derailleur is not positioned correctly. (When the chain is on the large chairing, the bottom edge of the derailleur should be about 3mm above the chainring) It is also worth looking at the derailleur itself, the inner edge may have been bent.