Access cup and cone bottom bracket
Refer to this guide to learn how to remove the cranks.
A lock ring on the outside of the left hand side cup will be an indication that the cup and cone bottom bracket is serviceable Turn this anti-clockwise to unlock the cup. This is easiest with a lock-ring spanner that fits the notches on the ring exactly, you can also use a universal tool with one tooth or a tap it round with a hammer and an old screwdriver. Remove the lock-ring.
Once you have removed the lock-ring, you can move the cup. If it has hexagonal flats turn it with a spanner. If the cup and cone bottom bracket has holes use a peg spanner.
Loosen The Left Side
Turn the left and cup on the adjustable cup and cone bottom bracket anti-clockwise. The left hand cup is the adjustable cup.
Remove the left cup and collect the balls from the left side. They may be loose or in a clip. Pull out the axle and note which way it fits it may not be symmetrical, one side may be longer than the other. Remove the balls from the other side.
The Right Cup
On most bikes the fixed cup – the one on the right – is screwed in on a left-hand thread. The exceptions are some old Italian and French bikes. The fixed cup may have two shallow flats or be hexagonal. There’s a bike-shop tool that locks a socket onto the fixed cup to turn it, and various spanners that fit fixed cups. As a last resort you may need to partially strip the frame, clamp the cup in a vice and twist the whole frame.