Need Generator Advice Please

I'd need your collected expertise about a generator.

I have a cheapo chinese petrol generator. Its rated output is 650W and 800W peak.
I have measured the output voltage and its OK at 241volts (I'm in the UK) and my kill-a-watt meter says the frequency is 52Hz. The mains here measures 49.9 or 50.0Hz dead on.

Is this safe to run a small fridge freezer (It draws 120W - I've checked) or is the output from these things "dirty". It does work but is it ok to run for a couple of hours say twice a day if the power goes out?

That's only 4%, won't hurt anything especially a motor/compressor.
An old analog plug-in clock with a motor (does anyone besides me have one of those anymore??) would run a touch fast.

If there's an easy way according to the instructions to adjust the speed, try it if you feel like it.
If not, don't worry about it.

Likely as the generator is loaded up it will slow down, thus reducing the voltage and Hz. Although it is close enough that it shouldn't matter.

Some electronics react poorly to a lousy waveform. The neighbors bought a large Coleman (cheapish) generator to keep their heat running during a storm. First time the power went out they fired it up, and the electronic control board for the furnace failed in short order.

I have a pure sine wave intervertor & leisure battery to run the electrics on my gas central heating - Its got a few circuit boards that I don't want to fry.
Its just the fridge I was wondering about - I assume it would be OK - but there's nothing like the collected expert opinions you find on CPF!

My old refridgerator would have been fine but the new one has electronic controls. I would be concerned if it's a newer model.