It starts but no power and the rpms will not come up

When you switch the ECO switch on your generator to the higher revving setting, the generator's motor should increase its RPMs in order to handle the increased load. However, if the A/C power cuts out and the motor starts revving high, it could be an indication of a problem with the generator's control system or a mechanical issue.
It is possible that the control system is not properly adjusting the generator's RPMs in response to the increased load, causing the motor to rev too high and shutting off the A/C power.
It's also possible that the generator's governor, which controls the RPMs, is not working properly, and is not able to adjust the RPMs to the correct level.
Another possible cause could be the generator's voltage regulator or control circuit, which may not be functioning properly.
It's best to have a professional technician diagnose the issue. They will be able to identify the specific cause of the problem and make the necessary repairs.
It's also important to make sure that the generator is being operated within the manufacturer's specifications and guidelines to avoid any damage or unsafe operation.

read you user manual but most small gen sets on starting come up to full rpms and stay there regardless of the load situation
it is the rpms that maintain the output voltage and cycles that has to be correct for when a load is suddenly applied

Ask a local mechanic here ,as they very rarely give problems ,now is this the three cylinder engine or the 4 as their is a difference as to trying to you some idea as the problem and stop revving the engine up as you WILL KNACKER IT UP

Possible fuel pump about to die. They will work if revs kept up

take it to autozone and have your alternator tested........

there is possibly a rev limiter( governer) at the upper end, which will drop one or two cylnders

make sure your not overloading the power and Amp's out put. you'll also my need to have your set re-calibrated. most tags show, 3600 rpms at 60 hz 120\240 no load. over time you'll ether loss or gain rpms which well directly affects your power output. let me know. good luck

Check for a clogged catalytic converter.

if the problem is when u go into gears it could be the clutch is going out. when it slips i can cause reduction like that. after you accelerate the clutch has time to engage and will provide power. the clicking sound is something diffrent. try charging the battery not just jumping it. if the car doing the jumping is not providing the right amount of power it wont start.

Does temp gauge go up when this happens ? When was fuel filter changed last? If not recently, I'd start there.