Step one – Set the 3-speed shifter to the second gear.
Step two – Looking through the chain tension nut hole in the rear axle you will see a toggle chain. The axle and toggle chain will impact the quality of the gear set.
Step three – To fine-tune the toggle chain and axle, wind the barrel adjuster in or out.
N.B Small adjustments will make a big difference.
Step four - The edge of the bar section of the toggle chain should protrude 1mm (see picture below) from the edge of the axle. Viewable from the chain tensioner nut.
Once happy with the barrel adjustment and relative cable tension, lock it off using the locking ring.