Unfortunately, the OP hasn't been back since 05/2014. He may not reply.
What are you experiencing and what have you done so we can all go down the path.
Same sort of issue. Petrol 3F on petrol and LPG (carb). When cold starts fine with choke, idles fine with choke. Take off fine and as I try to reduce choke after 2-3 mins will start to hesitate and miss at @ 1500-2000rpm. No power. Revs drop and will cut out. Runs fine when warmed up.
Have recently had carb settings checked and according to the mechanic settings were ‘miles out’ Not sure if I’m knocking the choke closed too early now it’s been tuned or have a vacuum leak somewhere or PCV issue as the OP had.