Lawn Mower Carburetor Cleaning

Okay, I will assume you have tried cleaning the fuel bowl as per part one of the guide, without success. Now you need to remove the carburetor, clean it and replace carburetor gaskets if they tear when removing the carburetor.

There are many different styles of carburetor, yours may look different. Some will have a choke, others will have a priming bulb. Some will be more challenging to remove than others. All will need to be cleaned at some point.

This post covers the subject of cleaning your lawn mower carburetor pretty well, but if you need more help, check out “Carburetor cleaning video”. It covers removing, stripping, cleaning, reassembly and refitting step by step.

If while following the above guide you found that you had no fuel flow, then proceed to fuel flow check below.

Preparation & Tips

  • Before working on your mower, remove the plug wire and shut off the gas. Check out mower repair safety video here.
  • It’s helpful to take pictures as you go, you’ll find them valuable when reassembling. Have a few rags handy and a container for fasteners. If you get stuck, check the out these videos.
  • Gas burns the skin, so I advise wearing surgical gloves and eye protectors. Gas stinks too, so make sure your in a well ventilated area. 
  • If you find your carburetor is corroded, don’t waste your valuable time attempting to clean it. Go ahead and replace it. You’ll find a list of all the most common types on this page “New mower carburetors”.

Tools You’ll Need To Clean Mower Carburetor

The correct tools for a task do two things, make you look like a pro and make the job move like butter. For carb cleaning there are a few tool that make the job easier. You’ll find all the tools I use here on the “Carburetor cleaning tools” page and if you need video help on tool identification, check out the tools video here.

Carburetor Removal

Plug wire off

Remove – Remove plug wire and turn off fuel as before. Loosen bolt on the fuel bowl.

Air filter

Remove – Remove the air filter, clean or replace before refitting.

Air filter housing

Remove – Loosen the air filter housing, two or three bolts usually. Have a suitable container for small parts. 

Carburetor gaskets

Photo – Pay attention to those gaskets and their locations. The gaskets are the paper type material sandwiched between the carburetor and engine.

These gaskets must go in the correct location and orientation.

Carburetor removal

Remove – Don’t be intimidated by all the pipes and levers. It is straight forward. Take your time, lots of pictures and you’ll be fine. A typical carburetor will have a fuel line, breather pipe, throttle lever and spring.

May have a choke lever, depending on choke system. It’ll look like this, dirty, if you have compressed air, blowing off the grime makes seeing components easier.

Air filter hosing

Remove – Remove the air filter housing bolts, and housing.

Gas line

Remove the gas line – use a screwdriver to pry it off. Remove the crankcase breather pipe.

Remove carburetor

Turn 90° – Holding the carburetor in one hand, turn it sideways to release the throttle link, spring and choke and lever. It’s now free and ready for the next stage, cleaning.

Stripping Mower Carburetor

Remove carb bowl

Strip – Move to a clean area, remove bowl.

Carburetor fuel float

Remove – Remove the float and needle, this is done by pulling the pin.

Carburetor float and needle

Inspect – The needle may have a rubber tip seal or the seal may be in the seat of the carburetor.

A worn seal turns pink. When seals wear they can cause too much fuel flow or no flow at all. 

Carburetor jet removal

Remove – Remove the main jet with a flat screwdriver, these jets are made from brass which is a soft metal and will damage easily. Be sure the screwdriver is a good fit.

Fuel air screw

Remove – Air fuel mix screw, but count the number of turns to remove the screw. You’ll need this info later when refitting the screw.

Emulsion tube

2 Types – Your jet may be one unit (integrated emulsion tube) or separate, meaning a jet and emulsion tube.

Cleaning Mower Carburetor

Carburetor cleaning

Cleaner – Use carburetor cleaner to clean all the passage ways and port holes.

Carb jet cleaning

Spray – Thoroughly spray all ports – the fuel inlet port, float and needle ports, air /fuel port, throttle plate, choke plate etc.

Emulsion tube

Clean – The dirt collects in the jet because it has small port holes which gas flows through.

Make sure all these ports are clean. Use a strand of wire to push through the holes. 

emulsion tube cleaner

Spray – Use your carb cleaner.

Bowl fastener

Gas Bowl Bolt – Some carburetors (B&S) employ an integrated bowl bolt and jet, these guys are famous for blocking and causing no starts, rough running etc.

If you have this type bowl fastener, its ports must be clean. A strand of wire brush works great for cleaning.

Idle jet

Clean – Some carburetors may have an idle jet, use the fine wire to clean it also. Check out this guide for more detail on idle jet cleaning, it’s a generator but the carburetor is identical.

Drain gas tank

Gas Tank – Drain the gas tank completely and change the fuel filter (if fitted).

Gas filter

Replace – Some mowers employ a gas filter inside the fuel line at the tank or inside the tank. Filters are covered in more detail below in the gas flow section.

Reassemble and Refit Mower Carburetor

Carburetor

Reassemble Carburetor – Remember to refit the air fuel screw to the same number of turns.

Fitting carburetor

Refit Carburetor – Remember to orientate those gaskets the correct way. Replace them if they’re damaged.

Fit the throttle, throttle spring and choke controls before fitting the gas line. Don’t forget to fit the breather pipe to the rear of the air filter housing.

Gas can

Gas Can – This bit gets overlooked, but it’s important. Clean out the fuel can. Check it for grit and if you’re not sure the gas is good, replace it and use a gas stabilizer (see video here on gas stabilizer).

Fill mower with gas and turn on fuel. You’re ready to mow, Nice work!

Gas Flow Troubleshooting

This section deals with two common gas flow problems – a lack of gas flowing from the carburetor, or too much gas flow. If you have either of these problems, you are in the right place.

The areas for consideration include:

  • Gas cap
  • Gas tank
  • Fuel lines
  • Fuel filter
  • Carburetor float needle seal

Lack of Gas Flow

If your carburetor isn’t supplying enough gas, it’s likely the problem rests with a lack of fuel caused by a gummed up float needle port. The needle seal commonly degrades and blocks the port. Replacing the seal may fix the problem, but often replacing the carb is a better fix. We’ll cover testing flow and the repair below.

Too Much Gas Flow

If your carburetor is supplying too much gas, it’s likely the float needle seal is worn. Replacing the seal may not fix the issue, often it’s better to replace the whole carburetor.

We’ll cover testing flow, common causes of gas flow issues and the various repairs next.

Testing Gas Flow

Carb drain

Remove Bowl – Remove bowl to test flow

Snow blower Gas off

Gas Tap – Turn tap on and off to control gas flow while testing

Gas cap

Gas Cap – When gas caps get lost, the MacGyver types usually find something to fit in it’s place. You know, old oil can cap or such.

The thing is, a gas cap has a vent which allows the gas tank to breath.

A sealed tank will slow or stop fuel flow, causing the engine to lose power or stall.

This is an easy test, remove the gas cap and see if the engine starts and runs OK. A common symptom of a sealed gas tank is – mower runs for ten minutes or so, then loses power and stops. If this sound familiar to you, check that gas cap.

Gas Filter – Check the fuel filter, there are a few different types, the common types include:

  • Bottle type are easy to check as most are see through. They can’t be cleaned.
  • In line filters are fitted inside the fuel line at the fuel tank. They can be cleaned and reused.
  • Tank filters are a mesh screen in the bottom of the fuel tank. They can be cleaned and reused.

To test flow through the filter, remove the fuel line at the carburetor, no flow suggests a filter/gas tank block.

Tank drain

Remove the out let pipe and check flow, it should by a constant steady flow.

Gas filter

Mesh screen in base of gas tank. Dirt in the tank is common and will slow or block gas flow. It may be necessary to remove the tank to clean.

Gas line filter

Not all mowers have a traditional style fuel filter, this is an inline filter.

Gas line

Fuel Lines – Problems with fuel lines usually revolve around leaks, which are easy to identify.

Other less common problems include: pinching of the line; blockage; breaking down of the inner wall.

Some manufacturers say that the alcohol in the ethanol blended fuels is damaging the rubber and plastic components of their engines. Manufacturers specify regular gas or e10.
They don’t recommend e15 and e85.

gas line

Check walls for cracking and leaks.

Snowblower float needle

Needle Seal – Float needle seals are made from rubber, they can be located on the tip of the needle or embedded in the needle seat. Either way, they wear over time and can break down causing a blockage.

Seal kits are available, but whole carburetors aren’t expensive or hard to fit, sometimes it’s best to replace the whole carburetor. 

Pink needle seal

Failure – Remove the float by sliding the pin out. Check the needle seal.

The needle tip seal turns pink when worn, some carburetors will have the seal in the carburetor needle seat instead.

Carb cleaning

Spray – Use fine wire to clean out the needle seat in the carburetor. Blow some WD carb cleaner into the needle seat on the carburetor.

Fuel should start to flow, if it doesn’t, remove and clean carburetor or replace with a new unit.

Related Questions

Where is the carburetor located on a lawn mower? The carburetor on a lawn mower is usually located towards the front of the engine opposite the muffler. The carburetor is positioned behind the air filter cover, the air filter is a black plastic square / rectangle cover.

Can you clean a carburetor with wd40? WD40 won’t be effective at cleaning a gummed carburetor. Carburetor cleaner is specially formulated to break down gumming deposits.