Generator won't start after sitting in the shed all winter — carb issue?

Same thing happened to me last spring with my Honda EU22i after it sat in the motorhome over winter. Classic carburettor issue — old petrol goes stale surprisingly quickly, and the lighter fractions evaporate leaving behind a varnish that gums up the jets.

First thing I'd try is draining the carb bowl completely. There's usually a small drain screw at the bottom. Let it all out, then put fresh fuel in and attempt a start. Sometimes that's genuinely all it takes.

If that doesn't crack it, the main jet is almost certainly partially blocked. On most inverter generators you can access it without pulling the whole carb off — a bit fiddly but doable on the driveway with basic tools. A carb cleaner spray and a thin piece of wire or a proper jet cleaning tool works wonders. Do not use a drill bit — I learned that one the hard way and had to order a new jet.

Going forward, there are two schools of thought:

• Run the carb completely dry before storage (let it stall itself out)
• Use a fuel stabiliser like Briggs & Stratton or Sta-Bil in the tank over winter

I've switched to the run-dry method and haven't had the problem since. Takes about five minutes and saves a world of bother come March.

What generator have you got? Some makes are genuinely more prone to this than others. The Chinese units with budget carbs seem to varnish up faster in my experience. Worth knowing before you start pulling things apart.

@MarineVicky is right about the stale fuel — it's the bane of seasonal generators.

One thing worth adding: the varnish deposits that old petrol leaves behind can block the pilot jet specifically, which is a tiny orifice. Main jet gets cleaned, engine seems fine at full throttle, but won't idle properly. Classic symptom people miss.

My Honda EU22i lives on the narrowboat — I run it monthly just to keep things moving, and I use Aspen 4 alkylate petrol for storage. Costs more but it stays stable for years and doesn't gum up the carb. Available from most agricultural merchants.

If you're cleaning the carb yourself:

• Carb cleaner spray through all orifices
• Compressed air to clear
• Check the needle valve isn't stuck

Genuine Honda carb kits are about £15 online if the jets are properly blocked.

Great points from @MarineVicky and @PennineNomad. One thing I'd add — before you even touch the carb, try running a bit of fresh fuel through with the drain screw on the float bowl. Sometimes that's enough to shift the gunk without a full strip-down.

If you do end up cleaning the carb properly, a can of proper carb cleaner and some compressed air through the jets usually does the trick. The main jet is almost always the culprit.

Going forward, Briggs & Stratton fuel treatment or similar stabiliser added before storage makes a massive difference — I run mine for about ten minutes after adding it so it works through the whole system. Sorted my old EU20i no end.

Drain the float bowl, squirt some fresh 95 in, and if she still sulks — Gumout carb cleaner from Halfords works a treat on my van's genny when I've neglected it since August. 🔧

@FellGraham good shout on the Gumout. I'd also check the fuel tap is fully open and the choke isn't stuck — sounds obvious but caught me out once with my old Kipor.

If the carb's properly gummed up, I've had decent results pulling the main jet and soaking it overnight in carb cleaner rather than just spraying. Tiny holes block with the tiniest bit of varnish.

Also worth fitting a fuel stabiliser going forward — Briggs & Stratton do one, widely available. Sorted my winter storage headaches completely. Chuck it in before the season ends and you won't be doing this next April.