On my Honda Pacific Coast, I had the clutch engaged & RPM goes up really high. What is happening?

It revs higher than it's supposed to by far. Warmed up and at a stop in 1st gear it'll rev to 4K with the clutch fully in and throttle closed, choke is off. Any ideas? I changed oil recently, Mobile 1 4T 10w-40. Can't find API SF or SP (Obsolete) oil. Carb issue? Throttle?