I just got my hands on a 150F for the first time today, so I am definitely no expert, but, on my full size Honda's, your symptoms can happen if you forget to install the clutch lifter rod or install the rod and lifter in the wrong order. Looking at the parts diagram for the 150F on this website, the obvious answer would be that you forgot to install the clutch lifter so when the "clutch lever" (inserted in the right crankcase cover) rotates it doesn't have anything to contact. If the lifter was, in fact, reinstalled, could any of those related parts in the parts fiche diagram be installed out of order?
http://partsfinder.onlinemicrofiche.com ... &A=154&B=2