[Closed] Stiff twist shifters

Hi guys

Looking for a bit of advice trying to sort out stiff grip shifters on my son’s bike. The lower the gear, the harder the shifter is to twist – I can manage it, but my 8 year old is struggling. Once in 1st, it’s then easy to shift up the gears.

The derailleur has ‘Shimano SIS 6 speed’ printed on it, no brand on the grip shift.

So far I’ve tried:

- Lubing all moving parts – shifter, cable and rear mech
- Checked cable – no kinks or twists
- Disconnecting cable from rear mech – shifter then clicks easily though all 6 positions
- Checked and adjusted derailleur high/low limits and re-indexed

No difference!

Appreciate any advise

Thanks