trx 250 wont start right

my 87 trx 250 x wont kick start but its getting spark and gas its bored to a 300 but the guy i got it from said its stock cam bottom end and carb(jet) ect it has intake and exhaust u can pull start it by dropping the clutch and aslong as you keep on the throttale its good expect the timing sounds off but when you kick it it sounds like its not getting something to help it start. i put a new plug i know the wires good sparked a screwdriver and it gets gas will flood carb every 20+ kicks so.
any help i would love i dont belive my timing could be off enough to not make it start but my shins starting to hurt from the random kick backs.