Normal preferred mix (airscrew) setting on a Kiehin is .5-1.5 range. 2T or 4T makes no difference.

Adjust for best running. If outside that range, a change in low speed jet may be used.

Thanks Copemech, the bike runs ok ticks over nicely but on removing plug looked rather black instead of biscuit only other thing is has stalled going downhill  a couple of times will try as you suggest.