Generator Carburetor Cleaning
In This Guide
If there is one repair that defines generator ownership, this is it. Generator carburetor cleaning is the single most common fix there is, because the single most common fault is a carburetor gummed up with varnish from old fuel. A generator that will not start, will not stay running, or runs rough after sitting is nearly always describing a blocked carburetor. Here is why it happens and how the cleaning is done.
Why the Carburetor Blocks Up
It comes down to what happens to petrol over time. Fuel left standing in a generator does not simply sit there, it degrades. The lighter parts evaporate and the rest oxidises into a sticky, gummy residue that eventually dries into a hard varnish.
That varnish coats the inside of the carburetor and, crucially, blocks the main jet, a metering hole finer than a pin that fuel must pass through. Once it is blocked, fuel cannot reach the engine in the right amount, and the generator will not run properly, or at all.
Signs the Carburetor Needs Cleaning
- The generator will not start despite fresh fuel and a good spark.
- It starts on full choke then dies when the choke comes off.
- It runs but surges up and down, or runs rough.
- It has been sitting unused for months with fuel left in it.
- There is a smell of stale, sour petrol from the tank.
What You Will Need
A basic set of tools covers it: a socket set and screwdrivers, carburetor cleaner spray, a container for the old fuel, clean rags, and often a carburetor rebuild kit with fresh gaskets if the old ones are perished. A thin wire or a strand from a wire brush helps clear the jet.
The Cleaning Process, Step by Step
1. Turn off the fuel and drain
Close the fuel valve, and drain the fuel from the tank and the carburetor bowl into a container.
2. Remove the carburetor
Take off the air filter housing, then the carburetor, noting where the fuel lines and linkages connect. A photo on your phone first helps reassembly.
3. Remove and clean the bowl
Take off the float bowl at the bottom. This is where varnish and sediment collect. Clean it thoroughly.
4. Clear the main jet
This is the critical step. Remove the main jet and hold it to the light. You should see a clean hole through it. Spray carburetor cleaner through it and pass a fine wire through to clear any blockage.
5. Clean every passage
Spray carburetor cleaner through all the passages and let it work. Blow them clear.
6. Reassemble with fresh gaskets
Fit new gaskets if the old ones are hard or damaged, reattach the carburetor, and reconnect the fuel lines and linkages.
7. Add fresh fuel and start
Fill with fresh petrol, open the valve, and start it. It should run cleanly.
When to Replace Rather Than Clean
Sometimes cleaning is not enough. If the carburetor is severely corroded inside, if the varnish has set so hard it will not clear, or if the machine is small and a new carburetor is inexpensive, replacement is the sensible call. On many portable generators a complete replacement carburetor is a modest part and quicker than an exhaustive clean.
Stopping It Happening Again
Run the generator under load for about 30 minutes every month, which keeps fresh fuel moving through the carburetor.
If storing it, either add fuel stabiliser or run the carburetor dry by closing the fuel valve and letting the engine stall.
Use fresh fuel, and consider ethanol-free petrol, which stays stable longer than ethanol blends.
Rather Have a Real Technician Handle It?
A Wildwood technician comes to your home, diagnoses the generator on site, and gets it running, usually in about an hour. More than 10,000 repairs completed since 2019, with flat rates quoted before we arrive so there are no surprises. When you need power back, you need it back now.