Yamaha G3-A (G1) runs badly

[CHASWAY]

G3A starts OK and runs very well on flat & level. Sputters at partial throttle and won't clime hills well at all - no power. New plug, fuel filter & new carb installed with little if any change. Also checked reed valve and exhaust flapper. Minor oil leak, but nothing bad. Noted just now that "jet sensor" hose connection at muffler is loose and may be leaking.
Any ideas? Thanks in advance.

[CHASWAY]

Hello, is there anybody out there that can help me?

[PaulRepairs]

Check for vacuum hose leaks. Might also be a float problem in your new carb.