The spare parts shows a spring 91 maybe you need to push down the knob first before turning to engage the link so it turns.
93 is a pin so that could be broken and if so it would need replacing.
This video shows a few adjustments.
Parts manual shows all the bolts to remove.
https://www.outdoorking-forum.com.a...ame/victa_imperial_chassis_4-strokes.pdfCheers
Max.