echo hca2500 wont run?

Hi every1. I have a echo hca2500 hedge trimmer. Ive changed the piston and ring, new gasket. Cleaned carb and exhuast. Ive managed to get it started on choke but wont rev or stay running on chocke. As soon as i put choke down i get a high rev then cuts out can be hard to get started after.ive fiddled about with h & L screws that helps a little bit. Any suggestions. I mean it was not running at all before i changed piston ect so must be getting some where.
I think maybe fuel maybe the diaphram.
Thanks liam