husqvarna 55 rancher?

put new piston,ring and cylinder,new fuel filter,fuel line and air filter,new sparkplug,hi test gas with xp husqvarna 2 cycle oil mixed to specs,changed gasket on carb it starts right up and idles fine but when i try to acelerate it bogs down and tries to stall,but when i let off gas it idles fine again i turned hi and lo mixtures screws every which way and nothing.Idle screws have plastic caps on them so I figured they dont want me messing with them is it worth taking them off and seeing what happens when I get more mixture screw to turn.