Generator keeps cutting out mid-cycle - is it the AVR or something worse?

Been following this thread with interest because I had something similar last year with my Honda EU22i — kept dropping out after about 20-30 minutes of runtime, almost like it was hitting a thermal cutoff.

In my case it turned out to be the spark arrestor partially blocked, which was causing it to run hotter than it should. Simple clean sorted it. But I know that's probably not everyone's scenario.

The AVR angle is interesting though — does the cutting out coincide with any particular load? I've noticed mine behaves differently when I've got the Victron Multiplus pulling hard versus just ticking over on standby. Makes me wonder whether it's a load-triggered fault rather than purely thermal or mechanical.

A few questions that might help narrow it down:

• Is there any warning beforehand (spluttering, rpm drop) or does it just cut dead?
• What load are you running when it happens?
• How old is the fuel you're using? I've had stale petrol cause some really odd behaviour

Also worth checking the low-oil sensor if yours has one — apparently they can give false readings and kill the engine even when oil levels are fine. Cheap fix if that's the culprit.

Has anyone on here actually replaced an AVR themselves? Curious whether it's a realistic DIY job or if it's one of those things where you end up making it worse without specialist kit.

Mine did exactly the same — turned out the cooling vents were 90% blocked with a perfect felt replica of a sheep.

@MoorRuss that sheep felt comment actually made me laugh out loud.

Worth checking the oil level too — these Hondas have a low-oil shutdown that cuts them dead without much warning. Catches people out constantly. Top it up even if it looks fine on the dipstick, because the dipstick readings can be fiddly if the unit isn't on perfectly level ground.

Also if it's consistently 20-30 mins, that's a very thermal-cutout pattern. I'd rule out the AVR for now — AVR issues tend to be more random/voltage-related rather than timed like that.

Clean the vents, check oil, run it again and see if the pattern changes.

@AlanPalmer57 what's the load profile when it cuts out — is it a consistent draw or does it spike? Worth knowing because a failing AVR tends to cause voltage instability before shutdown, whereas thermal cutoff is usually clean and silent.

On the EU22i specifically, the oil level sensor is notoriously oversensitive — even slightly low will trigger a shutdown with no warning. Had this exact issue on my boat last summer, thought the worst, turned out I was half a dipstick's worth down.

Also check the spark arrestor if it's been sitting unused — partial blockage causes heat to build up faster than it should.

What are you running off it when it cuts? If it's an inverter-charger like a Victron Multiplus, check whether the fault is actually being triggered from the generator's end or the charger rejecting the signal.

@MoorRuss has set the bar high with the sheep felt, I'll give you that.

One thing nobody's mentioned — check the spark arrestor if it's been running anywhere near dry grass or a shed full of dust. They clog silently and the engine just slowly suffocates itself like it's being passive-aggressive about working conditions.

Also worth doing a proper