250 Jtr Runing Strange And How To Set Carb Up Nad What Folk Seals

must just be a gasget to keep muck out i can see at the base of the head? im 99% sure the jets are clear iv dont them 3 times with carb cleaner and the air gun iv replace the intake manifold new plug new oil new air fillter still the same what about the reed block it has some gasgets on it from what i can see but unsure how i can test if thay are leeking. geting fed up now everyone says it wont be crank seals thay never go on the jtr engine? it did run a bit better last night when i had the fuel off as it was runing out it ran better and for 30 seconds when fuel back on but i tryed it again to see if it was too much fuel and nothing still the same would over fueling cause this? sorry for all the daft questions