Power generators Yamaha/Endress 4.2kVa Problem

Good morning friends, I have for some time a power generator with Yamaha motor (model MZ300- 10hp) and Endress power generator (model 4.2kVa, rated power 4kVa). The device has no high current connection, but only two white sockets. For some reason, the motor goes out when I connect devices that exceed 1800watts. 4kVa should at least result in a cosPhi of 1st and 18.3A/230V mathematically 4000W. Whether the 4kW can now be tapped at a power socket is sometimes there This is unfortunately not so, if I load both sockets with Flex etc, the power generator goes out anyway, as soon as the total load exceeds 1800W… oil new 10W40, oil level: OK spark plug spark good, color almost red: OK air filter new petrol fresh, petrol filter(mechanical sieve) clean carburettor completely disassembled and cleaned in the ultrasonic bath I have in idle set it to 225V by multimeter, speed according to measuring device 3200rpm. The old capacitor had according to capacity measurement 21uF instead of 25. I bought and installed a new one from ICAR 25uF: OK So slowly I doubt.. the engine runs quite quietly. If a device is turned on, it is only briefly minimal and continues to work in a slightly changed rhythm, but until the load is exceeded. Do you think I have something to do with the carburettor setting in combination m it the other adjustment screw under the tank simply wrong? Can this cause the problem? Thank you for your answers.