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

Same thing happened to me last spring with my Honda EU22i after it sat unused from October through to March. Classic stale fuel issue — the ethanol in modern petrol goes off surprisingly fast and leaves this horrible varnish residue that gums up the carb jets.

Few things worth checking in order:

• Drain the float bowl first (usually a small screw on the bottom of the carb) — if the fuel looks dark or smells sour, that's your culprit
• Spray carb cleaner through the jets and let it soak
• Check the pilot jet specifically — it's tiny and blocks easily
• Fresh fuel obviously, but worth adding Aspen 4T alkylate petrol going forward, it doesn't degrade the same way and is much kinder to small engines over winter storage

If the carb is properly gunked up you might need to pull it off and do a full soak in a parts cleaner. Had to do mine properly last year, took about an hour but saved buying a replacement carb.

Also worth checking the spark plug while you're at it — cheap to replace and easy to rule out.

One thing I do now is run the generator completely dry before putting it away for winter. Just let it run until it dies on its own. Bit of a faff but means there's nothing sitting in the carb to go stale.

What generator is it? Some have easier carb access than others. Has anyone tried those ultrasonic carb cleaners for this sort of thing? Been curious whether they're worth it.

ThistleWalker | 847 posts | ⚡ Solar & Wind Hybrid

@MeganFox makes a solid point about the ethanol, but worth mentioning — if the carb jet is completely gummed up, a simple drain and refuel won't cut it. I had the same with a Kipor last autumn and ended up needing to pull the carb apart and soak it overnight in proper carb cleaner.

Also check your air filter if it's been sat in a damp shed — spiders love those things over winter, no joke. Found a full web blocking mine once.

Going forward, either run it dry before storing or use a fuel stabiliser like Sta-Bil. I've had much better luck with the latter since it means the gen is ready to go immediately in a power cut rather than needing a full drain first.

VoltageViking | 312 posts | ⚡ Narrowboat Solar Hermit

Drain the carb bowl before winter storage — five minutes of faff saves five hours of swearing come March. 🛶

SussexBoater | 1,203 posts | ⚡ Floating Mostly Upright

If draining the carb feels too faffy, a squirt of Bradex Easy Start in the air intake works a treat for getting her fired up long enough to run fresh fuel through — learned that lesson the hard way when my generator decided to stage a protest in the middle of the Solent with everything in the 12v system flatter than my enthusiasm for winter boating.

TorDweller | 634 posts | ⚡ Batteries, Boats & Slow Miles

Something nobody's mentioned yet — the spark plug. After a winter sitting idle, I've pulled plugs out of my little Yamaha EF2000iS that looked like they'd been through a coal mine. Carbon fouling from the last few rich-running minutes before shutdown.

Whip it out, clean it up with a wire brush, gap it properly, and sometimes that's the whole story sorted before you even look at the carb.

Also worth checking the air filter — mice absolutely love making nests in generator housings over winter. Found one last February that had basically upholstered the thing.

Run through the simple mechanical checks first before you start pulling float bowls apart. Save the carb strip for when everything else checks out.

OldSailor75 | 89 posts | ⚡ Solar, Batteries & Wandering Roads

Had this exact problem with my generator last March — sat all winter in the motorhome hab bay doing nothing. Turned out to be the carb pilot jet completely gummed up. Even after draining the bowl like @VoltageViking suggests, old varnish deposits can block those tiny passages that a simple drain won't shift.

Worth picking up a can of proper carb cleaner spray and giving the jets a good blast through before reassembling. A fine strand of wire can help clear stubborn blockages too, though go carefully — you don't want to enlarge the jet orifice.

Also worth checking whether your fuel has any water contamination — winter condensation in the tank is real. A clear drain makes it obvious if there's separation happening.