Beware of travelling salesmen.
In the South West we also have Irish travelling salesmen. Allegedly they get a container full of cheap Chinese products shipped to Plymouth docks and somewhere they re-label the power ratings of the machines to about double. I've had them try to sell me stuff even offering to accept a cheque! In actual fact the generators are not a bad buy IF YOU KNOW WHAT YOU ARE GETTING but if they go wrong you will be on your own regarding the guarantee.
In actual fact ALL portable and semi portable generators can be very iffy indeed when driving into a non-resistive load or a load that has a built-in on-off switch. Some case histories include that of a farmer who was pumping away flood water caused by a blocked drain. The water pump had an inbuilt float switch! When the water was gone the pump switched itself off causing a power surge. The generator has never worked since and it appears to have shorted-turns as some voltage is produced at low rpm but none at full rpm! The generator was a decent Honda but even these can die like flies as portable power is NOT like the mains at home!
Another case involved a Nissan ND50 3KW generator that had a 6HP diesel engine. This was used by a person who had had his electricity cut off because he didn't want any bills! The generator was being used to power a 2.4KW automatic electric kettle. Although the generator had powered electric hotplates and kettles in the past it finally failed when the kettle boiled and switched itself off. Whilst a gas ring would have been simpler, cheaper and quieter the man had a very sensitive nose and he didn't like the fumes!
Variable speed power tools can also wreak havoc regarding voltage spikes as they chop the current on and off. This produces an effect that is analogous to water-hammer in a pipe. The solution to these problems is however simple and cheap. All that is needed is a double socket and a lamp using a 40W or 60W filament bulb NOT a low energy bulb. The bulb will snub the voltage spikes and prevent damage from occurring.
One generator that I repaired must have run for thousands and thousands of hours. It had failed as a result of vibration shaking everything apart. This was probably caused by its broken fan only half of which remained! A replacement fan from an old car alternator was adapted to fit and the broken wiring and metalwork were repaired. The capacitor in the "control box" was stuck down with silicon rubber sealant to prevent it vibrating loose again and thread-lock adhesive was used on the screws that had worked loose. The make was "Haverhill" and it used "direct compound excitation". The beauty of this method is that a fat capacitor sits across the output terminals and makes the generator virtually surge-proof and idiot proof. It was in fact built as a building site generator and it produces 110 volts. At the last count it was being used for lighting a barn near Holsworthy. The advantages of 110 volts are safety and the fact that the machine is not so attractive to thieves!
Voltage Dependent Resistors also known as ZOMs, VDRs or Spike Catchers can also be employed to prolong the lifespan of portable generators but the bulb method has a lot to recommend it. Note that attempting to weld with a portable generator can be extremely difficult. For a start at least five kilowatts are needed although ten or fifteen kilowatts are better. The old "buzz box" type of welder is not advised but instead a generator friendly inverter welder is more suitable as these usually have anti-stick current limiting which the generator will greatly appreciate. Good luck!