Villers Carb problem on a Forty - Help needed!!

[Skipper Billy]

I have returned to the Seagull flock after a brief affair with a H*nd* !!
I have bought a Forty plus in very good condition and it runs a treat up to about 2/3 throttle - beyond that it just dies like its too lean. Is that normal?? Its not that I want to run it at full bore but the point is that it SHOULD! Any ideas????