Aerox doesn’t want to start

I’ve bought an 12 plate aerox started first time with one kick but now I’ve put 17.5mm motorforce carb and now doesn’t start I’ve changed auto choke new fast flow fuel filter and still nothing

 

Too lean. Too rich? Just try a new plug first

 

Yeah I’ll try a new plug would a normal one do or a specified one? And it was running rich so turned it down

 

Just the same as whats in there now. I would hazard a guess its too lean as too rich normally starts easy then is a pig to get going.