Hi i am trying to repair a 14/ hp briggs motor. This motor has ohv where i have never had a chance to work on i am from old school and not used to this newer equipment. Here is the problem first he carb was overflowing with gas i took it apart and cleaned everything with parts cleaner and hoped i put it all back together correctly. Now it starts without overflowing the gas. Now the problem i have is that the air fuel mixture screw dose nothing it makes no difference where you screw it it has no effect.the only way the motor runs is if it is at full throttle if i try to run it any where in between it backfires and stalls out. If anyone could point me in the right direction that would be great if you need more info pleases let me know thank you for all your help

Sound like a clogged jet. Be careful if you use Carb cleaner to blow out jet orifices.(Eyes)
Float level may be important. The main jet will keep flowing if float is miss adjusted,
Touching side of float bowl or not closing.

Would The Valves Adjustment Have Any Thing To Do With This Also Any Idea On How Many Thousands To Adjust Them Too Thanks