Prise off any part which overlaps the two sides of the lighter

Remove any screws holding the two sides together. They are usually star head. I find that a 1.5mm flat screwdriver works fine

Split the two halves

Remove the tank and trigger but do not stress the wiring. Note the black gas regulator lever on top of the gas line and the black linkage below the gas line.

Disconnect the black linkage. You may have to disconnect the gas line.

Prise off the gas regulator lever.

This is the regulator lever removed. It needs to be put back but repositioned towards the minimum setting. An offset towards minimum of 45 - 90 degrees depending on how high you want the flame to be.

Note the regulator lever repositioned towards you, which is in the direction of the minimum setting

Put the tank and trigger mechanism back in place taking care to route the wiring and gas line away from moving parts and joints.

if the pivot wheel has become detached take care to align the white sprocket with it's guides.

Reassembly from here is the reverse of disassembly. Push the two sides together, do up the screws and replace any shrouds.

This is the new flame height on maximum. Maybe a bit much but a result in any case.