2004 rm 250 troubles

I recently purchased a 2004 rm 250 and I'm having some difficulties getting it to run good the motor feels like its going to foul a plug when the throttle is at 1/4 to 1/2 throttle ....so here's the run down i live in western mass about 1000 feet above sea level I have a pro circuit pipe with a 304 silencer vforce reeds (brand new) I'm running 50/50 c12 and 93 octane pump gas with maxima castor 927 at 40:1 the jetting I have is a 165 main with a 45 pilot , necj needle set on the position 2 and a 7.0 slide also I should mention the guy I bought it from said the cylinder was ported and polished by bills pipe I had the cylinder apart to put in fresh rings and the porting looked sloppy I believe ...could this not be a jetting issue and maybe he tried to port and polish this himself ??? Also my friend said maybe I could have a solenoid issue on the carb ??? I'm trying to get to the bottom of this issue the bike runs good on top but in the middle it's completely and terribly flat. Can anyone out there throw me some advice