Honda HRX215 reduced power under load. Valve problem?

I acquired an HRX215 master series mower. It was sold as non-starting. I cleaned the carburetor and the mower now starts on the first pull. However, it does not have power under the load. This is a clutch blade machine with a hydrostatic transmission. Both work great. However, when engaging the clutch the the mower doesn't have any power. I tried resetting the governor to bump up the RPM. It help but the engine still feels very weak. The engine clearly doesn't have power.

Could it be that...

Honda HRX215 reduced power under load. Valve problem?