My Mt.bike's rear gears wont change!!?

Question

the bike is a haro it has 3main gears and seven rear gears/cogs,and it only stays in the smallest cog. when i try to shift down the pressure to do so is great, but when i up shift its little to no pressure, but wheather i put the gear slection up or down the chain wont come off the 7th(smallest) gear.

Answer 1

I hope you are pedaling while you are shifting.

Answer 2

The bolt holding the gear cable into the rear derailleur might have loosened, hence the cable will not be pulling the derailleur and so not moving the chain onto a larger sprocket.

Or...The gear cable has stretched a significant amount, but I've never seen a gear cable stretch to such extremes.

Or...The right-hand gear shifter might be faulty.

Answer 3

same as before,change to small front ring and ride it.