Throttle position has no bearing R.P.M.

[Dayn]

Have a Briggs Stratton Sprint 3.75 engine that stays at same rev speed no matter what position the throttle linkage is set at..wide open or idle it barely creating any r.p.m. think might have partiallky clogged carb..it is MODEL 98902- TYPE 011001- CODE 95052451..off Murray OHIO push mower mfg.1995..I gave 35 bucks for it 3 years ago and getting it going for upcoming lawn maintenance has been a challlenge..the air filter was rotted need one and probably need tank carburetor duo since lots of debris inside tank I see