I've got a small but annoying problem with my gears.

When I shift from a large cog to a smaller cog at the rear, it will not move unless I move two gears at a time. Whilst if I shift back up the gears it moves okay one gear at a time.

I've tried adjusting it and I know it must be something slight but I cannot quite get it right.

Can anyone help ?

Thanks Ouch !

Maybe I should point out that I'm talking about my Kona Blast Mtb.