Gear change on a GS160 with PX engine

Hi All, 


I have just recently got back into Vespas after a long break, and have been busy working on a project to fit a Parmakit 177 P150X engine into a GS160MK1 (which didnt come with a GS motor!)

Everything is going reasonably well, but on cabling up the engine I realise I have trouble to get into 3rd and 4th gear.. it could be a bad selector box which is making it worse (new one on the notepad already!), but it occurs to me that the standard GS160 gear change pulley in the headset is too small to fully operate the larger wheel on the PX gear selector.

Is this a problem anyone else has faced? and what was the solution? I heard there may be a custom PX based pulley but I cant seem to find any, or much mention of this issue.. so is it just me?


Thanks in advance