Small Gasoline AC Generator Theory

Is there a mechanical speed governor fitted?

The key to regulation in your schematic, is the "condenser". This link, although not an endorsement, can give more information: http://www.gillettegenerators.com/klnpower/kpower01.html

Typically that circuit belongs to a mechanically throttle regulated sub 4 kVA genset.

It's about 'exciting' the ac output, not regulating it, as such.

So; it will not produce current if the capacitor (condenser) is off-spec, or dead.

It will produce no volts if the rotor 'rectifier' is faulty. (the one in parallel with the resistor and coil)

And produce different Hz (and volts) if the governor is out.

And, it may fail to 'excite' if the rotor 'residual magnetism' (or the small magnets often attached to the rotor) is/are lost.

Thank´s for the replays.
The reason of my posting was to learn how to alter the frequancy of my HYUNDAI 800W 220V 50Hz gasoline generator to 60Hz. Actually, the schematic I posted is not for this model but it is the only one I found on the Internet since Hyundai provides no schematics nor any tech instructions. I managed to adjust the speed governor to 3600RPM all right but the voltage rised too high. Then I reduced the capacitor from the original 12uF to 7uF and everythig was fine but only with 600W resistive load. With 40W load or with no load at all the alternator does not exite itself and produces no power. I reached 240V 55Hz with 10uF cap but I still would like go to 60Hz.

Buba, speed sets Hz and you should say why what you want to know - first up.

Playing with the capacitor will mess up the relationship with the windings.

If it says 12uf on the can, then it needs to be 12uf.

Measure it with a capacitance meter [nowadays $30] and see if it is 12. If so put it back.

Small generators are commonly 5% over V and Hz lottery, on light loads.

Most appliances don't care. So why are you chasing exact accuracy?