Honda Lawn Mower won't Start

Honda make reliable, well designed and constructed mowers. You bought one, so you already know this.

 

So why won't your Honda mower start? The most common reason a Honda mower won't start is because the carburettor is gummed up. Other possible causes include:

 

  • Fuel Valve Off
  • Choke Not On
  • Bad Gas
  • Plug Wet/Faulty
  • Plug Wire Off
  • Air Filter Blocked 
  • Carburettor Fault
  • Coil Fault
  • Bail Lever/Ignition Fault
  • Flywheel Timing (Shear-key)
  • Sticking Valve
  • Low Compression

I work on lots of Honda's and major failures are very rare. Let's begin by doing some basic checks. Sometimes this will solve the problem or at least point you in the right direction.

 

This guide will assume that components such as pull cord, throttle levers etc, are working OK. If you think that this is not the case, I wrote a guide that covers all pull cord common problems - check out "Pull cord troubleshooting".

Check the Basics

Is the oil level low? 

Is the gas turned on?

Is the gas fresh? 

Is the choke on and working? 

Is the air filter clear and dry?

Is the plug wire on securely?

Is the bail lever on and working? 

 

That's all the easy stuff checked, now we'll dig a bit deeper. Bad gas has become a real problem, especially in Honda's, the carburettors are so sensitive to contaminated gas.

 

In the workshop, I find the majority of Honda mower engine problems are related to bad gas. Common symptoms of bad gas include, Honda won't start, engine starts then dies and engine surging.

 

So, over the winter months I recorded a how to DIY video course. The videos cover diagnoses, removal, strip-down, cleaning, reassembly and refitting of a Honda carburettor.

 

The videos are designed for beginners and I start right at the beginning, you follow along beside me step by step.

 

By the end of this course you'll have saved $$$, learned a ton of new skills and have a sweet running Honda. Link to video guide "Honda lawn mower surging".

Oil Level

Some Honda mowers won't start if the oil level is low, this isn't a flaw, it's designed that way to protect the engine. It's good practice to check the oil level every time you fill the gas tank. Check on level ground and with all wheels set to the same height.

 

The Honda will take .58 of a quart (.55lt) from empty. If your in any doubt about how to check the oil, you'll find this guide helpful - "How to check lawn mower oil".

 

A Honda won't like to be over filled with oil either, this can damage the engine, cause it to smoke, leak oil and sometimes not start.

 

Mower Oil Level check

Check Oil

Gas Level

Is there gas in the mower? Sometimes the obvious is the solution, and as Sherlock Holmes says "we should check a fact is indeed a fact". The customer may have filled the gas tank with what they thought was good gas.

 

At my shop I have found many strange concoctions - diesel, water, white spirits, vinegar and of course last years gas makes a regular appearance in the tank. 

 

The fix for bad gas - drain the tank and clean the carburettor. You might find this guide helpful, it walks you through the whole process - "Carburettor clean out".

 

Mower gas tank

Fresh Gas

Gas Tap On

The fuel tap is used to cut fuel supply to the carburettor. I tell my customers to turn off the fuel when the mower isn't in use. It's easy to forget to turn it on. Honda fit their fuel tap on the right hand side of the engine when viewed from the front of mower. 

 

This short guide with pictures shows you where your gas tap is, what it's for and when to use it. Check out "Where is my lawn mower gas tap".

 

Honda mower gas tap

Gas On

Air Filter

A blocked air filter will prevent the mower from starting. The Honda air filter needs to be kept clean, check it every 25 hours of use, and replace every 100 hours. Honda fit tool less air filter covers, makes cleaning super easy.

 

The air filter cover is on the right hand side of the engine, opposite the muffler. Cleaning the filter with compressed air would be nice, but banging on the ground will do just fine. 

 

This guide will help you service your mower in under an hour - "Mower tune-up".

 

mower air filter

Clean

Plug Wire On

It's easy for the plug wire to come loose, happens all the time. The plug wire lives right at the front of the engine, so it's banging into shrubs and hedges and the like. It's the black wire with the rubber boot on the end.

 

Just make sure it's making good clean contact with the plug. Bad or no contact will give you a no start.

 

Carburetor primer

Wire On

Choke On

I meet lots of customers who don't know how to use the choke correctly, and I don't blame them, likely they weren't shown by the retailer. The choke is used to start a cold engine. A cold engine needs more fuel than a hot engine, so the choke creates a richer air fuel ratio.

 

Some Honda's will have the traditional choke lever and more modern mowers will have the auto choke set up.

 

Not sure if your choke is working? This guide will walk you through the testing procedure, it's simple and includes pictures - "Choke testing".

 

If your mower doesn't start on the 3rd attempt it's very likely that the plug is now saturated in fuel - condition known as flooded. The fix is to remove and dry the plug or leave the mower for 30 minutes to dry out, and then try again, this time without choke.

 

If your in any doubt about how to start a mower, this guide covers it all, you'll be a pro 2 minutes from now - "How to start a lawn mower".

 

Honda mower throttle

Choke On

Some Honda mowers are fitted with auto choke and so the choke won't be controlled by the lever.

Bail Lever On

The Bail lever or dead mans lever, is a safety feature. Its function is to stop the spinning blade within 3 seconds of release. It does this by shutting the engine off and applying a flywheel brake. If the bail lever isn't held the mower won't start.

 

This guide will walk you through testing for spark and how to change a coil, it's simple - "Ignition system testing".

 

Honda mower bail lever

Bail On

Only some Honda mowers will have the stop/start controlled by the bail lever.

Other Honda's have the stop/start control built into the throttle lever.

Check For Bad Gas

Bad gas is the number one cause of no starts. Your gas could be clean but stale, and mowers don't like stale gas.

 

Gas starts to go off after one month, it losses its ability to com-bust which causes poor performance and misfiring. When it goes completely stale, usually around 3 months old, it starts to solidify.

 

This has become such a big problem, last season I got a ton of questions about carburettor cleaning.

 

 

 

It's simple to use, just dump one ounce of gas stabiliser into 2.5 gallons of gas, fill your gas tank and run the engine to mix it throughout the fuel system, that's it. This stuff will protect and clean your fuel system and can be used in all gas powered kit including 2 stroke engines.

 

You may find this page useful, it lists tools that make cleaning the carburettor a ton easier. "Carburettor cleaning tools"

 

I use a brand called Sta-bil gas and you can check it out on Amazon.

 

 

 

 

Mower carb Mower carb

Gumming

It's a carburettor killer, using a gas stabiliser will prevent a lot of problems.

Try The Gas Shot

Your engine needs fuel, spark and compression to start. Fuel, Spark and Compression are broader areas than their title suggests. Testing will take into account the complete system, for example fuelling is more than just the gas, it includes carburettor, tank, air and fuel filters, gas line, intake manifold, etc.

 

The most likely cause of a no start Honda is fuelling, and so we will start there. Next most likely is spark and least likely of all is a compression issue. 

 

To quickly test for a gas issue - by pass the fuel system. We do this by pouring some fresh gas directly into the carburettor.

 

The symptoms of bad gas vary: mower won't start; mower runs rough; runs but only with choke; splutters when cutting on a slope; dies when cutting grass; lawn mower starts and then dies.

 

Honda mower air filter

Remove

Remove the air filter, by pressing the two plastic tabs.

Honda mower air filter

Gas

Tilt your mower over and pour a cap full of gas into the carburettor.

Honda mower Honda mower smoking

Pull

Attempt to start the mower in the normal way.

There are two possible outcomes -

(1) Mower attempted to start or started - tells us we have a fuelling fault.  Check out "Choke system"

(2) Mower made no attempt to start - then we've likely eliminated a fuelling fault, and the fault will probably be a lack of spark. Check out "Ignition system check"

Does Your Honda Need A Tune-up

Your Honda engine should be serviced at least once per season, ideally in the spring. Tune-up kit includes: oil; plug; air filter; fuel filter (if fitted); new blade (optional).Your Honda engine will likely be a Gcv 160 or Gcv 190cc.

 

The service kits will be identical, however Items such as carburettors and blades will be different. 

 

Check out "Mower tune-up guide".

 

Buying the tune-up kit on line is easy. You can find your model code right at the base of the handlebars, on the body of the mower. Honda mower engines are very common and so you won't have a problem getting a tune-up kit to match.

 

Check out "Honda parts look-up". 

Honda mower engine

Tune-up

Kit should include, oil, plug and air filter. Replacing the blade is optional.

Honda mower engine Honda mower engine code

Model Number

Test The Choke System

Your mower won't start if the choke is faulty. In this next step we need to be sure the choke system is working correctly. The correct starting procedure for a cold engine will require giving it extra gas to enrich the fuel/air mixture which a cold engine needs for a smooth start.

 

Choke Testing

Honda use a choke plate type system to achieve this fuel enriched condition.Your mower won't start if the choke is faulty.

 

The manual version which will have a throttle lever to control the choke.The auto choke version won't have a choke lever. Instead, a thermostat mounted close to the muffler heats and pushes on a lever which opens the choke plate.

 

Honda mower throttle lever Mower carb

Choke On

Remove the air filter, this allows us view the choke plate.

If you have a manual choke control, move throttle lever to full choke position to start a cold engine. Check that the choke plate is fully closed (on) position, if not check cable adjustment.

Your Honda may have auto choke. If so, when cold, the choke plate should be closed, as per picture. If not, move plate by hand to see if its stuck. If sticking, try WD40.

If you found no issues with your choke system, move on to "Gas Bowl Clean".

Honda mower throttle lever Mower carb

Choke Off

When the mower has started, the throttle should be moved to the run position. Check that the choke plate is in the fully open (off) position as per picture. If not, adjust cable.

A sticking choke will run poorly and puff black smoke from the muffler. Your Honda may have auto choke. If so when hot, the choke plate should be open, as per picture. If not, replace choke thermostat at the muffler.

If you found no issues with your choke system, move on to "Gas Bowl Clean".

The Problem With Ethanol Gas

Honda recommends not using fuels with more than 10% ethanol. Ethanol is an alcohol fuel made from sugar, corn and other plant materials. This alcohol is then blended with gas to make ethanol.

 

It's claimed that the alcohol content of the ethanol will damage the carburettor's rubber seals and hoses.

 

E15 contains 15% ethanol and is not OK to use in Honda mower engines. E15 burns hotter than other fuels, your mower is not designed to run at these temperatures. Ethanol absorbs moisture from the atmosphere.

 

If the fuel is left in the mower over the winter, the moisture collects in the carburettor. The water will often corrode and leave a varnish type deposit which blocks up the ports. This is what causes the poor running/no start. 

 

Gas Stabiliser

Regular gas older than three months is stale unless you use a fuel stabiliser. Ethanol fuels are stale after one month. Gas is the number one reason for a no start or poor running.

 

Using a stabiliser will prevent lots of these problems. As you know, you don't have to use the stabiliser all season, but do use towards the end and when winterising the mower.

 

Treating your gas will save you downtime, hauling your mower to the shop and  $$$ in repair costs.

 

Gas stabilizer

Stabiliser

Just dump a few drops into into the gas tank, and run the engine. Simple!

Try Cleaning The Gas Bowl

Often just cleaning the gas bowl does the job. Removing the carburettor is a bit of a mission, so if cleaning the bowl gets us out of trouble, it's worth trying. If you suspect stale gas, then you'll need to drain the gas tank also.

 

You can drain the tank by removing the fuel line, I use a Briggs and Stratton oil extractor, you can check the price on Amazon.

 

In other cases you'll need to remove the carburettor, clean it thoroughly and drain the gas tank. Honda mowers are fitted with different size and types of engines.These engines will be fitted with different types of carburettor. Your carburettor may look different, but the process is the same. 

 

In this part of the guide I will remove just the fuel bowl, spray in some carburettor cleaner. You can find your fuel bowl behind the air filter. You don't need to remove the air filter housing to access the bowl.

 

Remember if your gas is older than three months, it's stale. So cleaning the bowl won't always make it go. You may need to drain the tank, carburettor bowl and fill with fresh gas. If this works out for you great! 

 

If not, check out this guide it covers the whole process and includes pictures - "Carburettor clean out".

 

Mower plug wire Honda mower gas tap

Pull Wire

When working on your mower remove the plug wire and turn off the gas. This prevents a spill.

Mower plug wire Honda mower gas bowl Honda mower gas bowl Honda mower gas bowl

Remove

Removing the 10mm drain bolt will drain the bowl, but won't clear the grit from the bowl. I like to remove and clean the fuel bowl.

Drain the fuel tank, now if you need to.

Turn on the gas to check fuel flow, if no fuel flows from the carburettor as per picture, move on to - "Fuel flow test".

Spray some carburettor cleaner up at the main fuel jet before refitting the bowl.

That's it, test mower and if it's still not right, check out "Carburettor cleaning".

Try Cleaning The Carburettor

Okay, I will assume you have tried cleaning the fuel bowl as per the above guide without success. Now you need to remove the carburettor and clean it.

 

Have some carburettor cleaner or similar, container for nuts and bolts and take lots of pictures to help you remember where levers and gaskets are positioned.

 

There are a couple of different styles of carburettor, yours may look a little different, but the process is the same. Some will have a manual choke, others will have auto choke. Some will be more challenging to remove than others.

 

Here's some of the tools I use to clean carburettors, they'll make the job a lot easier. "Carburettor cleaning tools".

 

If you find carburettor corrosion or it's badly gummed up, go ahead and replace it, because nobody likes doing a job twice. Replacement carburettors are not expensive. 

 

Note that Gcv 160cc and Gcv 190cc carburettors look the same, but are different. So when ordering have your model number handy.

 

Check out "Lawn mower carburettor types", it's a list of common type carburettors

 

Strip Down

Removing a Honda carburettor can be a little challenging. It's not complex but there's lots of gaskets which must be replaced in the same order.

 

In addition, the air filter housing bolts are also the carburettor bolts, so the challenge is to align gaskets, carburettor and air filter housing before threading the bolts.

 

Take lots of pictures of gaskets and carburettor link positions. Lay out your gaskets in an order that makes sense to you. All you really need here is patients.

 

Honda mower air filter Honda mower air filter housing Honda mower carburetor

Remove

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

Remove the air filter clean or replace before fitting.

Loosen the air filter box/carburetor bolts (3) - two carburettor bolts and one air box bolt.

Have a suitable container for small parts.

Fitted to the back of the housing is a pipe which just pulls off, it's the crankcase breather.

Honda mower carburetor Honda mower carb

Air Box

Take pictures of gaskets and locations.

Remove 3 bolts and take more pictures of throttle link locations.

Set any loose gaskets aside, and in order.

Some will stick to the carburetor or other components and that's fine don't remove them.

Gaskets must be fitted in the same location and orientation.

Honda mower carburetor Honda mower gas line Honda mower gas drain

Drain Gas

If you haven't already, drain out the old gas.

Use a long flat screwdriver, prise off the gas line, removing the gas cap speeds up the draining process.

Best to do this outside, gas stinks.

Honda mower carburetor Honda mower gas line Honda mower gas line Honda mower gas drain

Links

With the fuel line removed, you can turn the carburettor on its side to  unhook the choke, throttle links and spring.

Don't be tempted to bend the links.

With the carburettor free, move to a bench.

Honda mower carburetor Honda mower gas line Honda mower gas line Honda mower gas line

Strip Down

Move to a clean area, and remove the bowl.

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

If your bowl is very corroded, go ahead and order a new carburettor as repairing rusty carbs isn't worth the effort.

Check the needle tip, a worn tip turns pink.  When these seal tips wear, they can cause either too much fuel flow or no flow.

Replace needle or replace whole Honda carburettor.

Honda mower carburetor Honda mower gas line

Screw

Remove the main jet retaining screw. These guys are made from brass which is a soft metal.

So a proper fitting screwdriver is essential, otherwise the screw will be damaged.

Honda mower carburetor Honda mower carburetor Honda mower carb Honda mower carb jet

Jet

The brass main jet seen in the top picture, needs to be pushed free.

Take a suitable screwdriver and push on the jet, to free it.

It may need further encouragement, tap on the jet housing as per picture, until jet is free.

Honda mower carburetor jet Honda mower carburetor

Clean

Clean the port holes of the jet and retaining screw  thoroughly. I use a strand of wire plucked from a wire brush.

The holes may look clean, but are dirty. After you have cleaned them, they will be noticeably bigger.

This allows more fuel to flow to the engine.

Honda mower carburetor Honda mower carburetor jet

Spray

Spray all carburettor ports liberally with carburettor cleaner, fuel inlet, float needle seat, jet, throttle plate, choke plate and any other ports you can see.

Honda mower carburetor Honda mower tank Mower gas can

Rebuild

Reassemble, fit the jet, screw, float and needle. Careful when fitting the gas bowl, the large o ring can become pinched, apply some oil to help it seat.

Don't over-tighten the bowl, it causes it to leak.

Refit carburettor to the mower. Take special care when fitting the gaskets. Check your reference pictures.

This bit gets overlooked, but it's important. Clean out the fuel can and your gas tank.

Check it for grit and if you're not sure the gas is good, replace it.

Fill with gas and turn on fuel. Fit spark plug wire, and you're good to go.

Check The Gas Flow

This section deals with a lack of gas flow from the carburettor. The areas for consideration are: gas cap; carburettor float needle seal;fuel filter; fuel tank; fuel lines.

 

If you have too much gas flow, the float needle is at fault, and yes you could replace the needle but often this doesn't fix the problem. I like to replace the whole carburettor. This page list popular carburettors "Carburettor types"

 

Small engine mowers use gravity flow to get fuel to the carburettor. Meaning the fuel tank should be higher than the carburettor. To test for flow make sure you are on level ground and have a minimum 1/4 full fuel tank.

 

Common reasons for no fuel flow are bad gas cap and dirty float needle seals.

 

Mower gas flow Mower gas cap

Gas Bowl

The best way to troubleshoot no fuel flow is with the fuel bowl removed.

A fuel tank needs to breath. When fuel leaves the tank it needs to be replaced with air.

A sealed tank will prevent fuel from flowing.

Remove the cap and check flow.

Mower gas flow

Gas Tank

Honda use a mesh screen in the bottom of the fuel tank to filter the gas.

Look in to the gas tank, which is easier when it's empty, and check the filter for grit. ​​

I use a suction pipe to clean the bottom of the tank, however sometimes you need to remove it to clean it thoroughly.

Mower gas tap

Gas Tap

Check if the gas tap is the problem, remove the gas line to the tap and check flow.

Honda mower carburetor float Honda mower carburetor needle Honda mower carburetor needle

Needle

Remove the float and check the needle seal.

Use fine wire to clean out the needle seat in the carburettor. I use a strand from a wire brush.

Blow some into the needle seat on the carburettor.

Fuel should start to flow.

Test The Ignition System

Spark is just as important as fresh gas. When it comes to spark, your plug is the first component to check. So be sure to have a good plug on hand. In this section we will check the: plug; plug wire; coil; coil control wire; bail lever.

 

The test will require removing some covers. You don't need any special tools to complete this test, but I prefer to use a spark testing tool.

 

It easier to check solo and loads the coil to spec, I use the Oregon in line tester and you can check the price on Amazon.

 

You'll need to check the spark plug gap also, I use a gap tool which you can find on "Small engine repair tools" page. 

 

Mower repair tools Mower spark plugs

Tools

For this test you will need a spare plug, any plug will do for the test.

But only fit Spark Plug (BPR6ES) to a Honda gcv 160 and 190.

You will also need a plug spanner, insulated pliers and a very brave helper, who can withstand extremely high voltage....... I'm Joking, it's only moderately high voltage.

Mower spark plugs Mower spark plugs Mower spark plugs

Spark Test

Note: The best way to test spark is with the In Line Spark Tester tool or similar, as it will load up and stress test the coil.

Remove the plug from the mower and put the plug wire back on the plug. Now hold the plug against the metal of the engine using the insulated pliers, take care to ground it well.

The helper now attempts to start the mower while you observe plug spark. You should see a bright blue spark. If no spark, try the new plug.

There's 2 possible outcomes:

(1) No spark with either plug. If so keep reading.

(2) Spark is good, if that is the case, check out "Carburettor cleaning" and if that fails run a compression test.

Mower coil wire Mower plug wire cap

Damage

If you have no spark or your spark is poor you could have a faulty coil; spark plug wire; coil cap; short circuit of coil control wire or poor bail lever cable adjustment.

Look for obvious signs of damage.

Mower throttle lever Mower on/off switch Mower cable adjustment Mower cable adjustment

Throttle Stop/Start

This is the throttle stop/start control type.

Most Honda mowers are fitted with stop/start control at the throttle lever and some have the bail lever stop/start, which is covered next.

The stop/start coil control switch see here, is mounted beside the carburetor.

Check that the switch is being operated by the linkage when you set the throttle to the start position.

If not, adjust the cable at the throttle lever.

Mower on/off switch Mower plug test

Testing Throttle Switch

Truthfully, I don't usually test these switches, because they don't give trouble. So at this point I would go ahead and fit a new coil.

However you can test them by un plugging and repeating the spark test performed at the start of this guide.

If after running the test, the plug now sparks, replace the switch.

Still no spark, go ahead, move on and replace the coil.

Mower throttle lever Mower on/off switch

Bail Stop/Start

This is the other type stop/start system, the bail lever, and is connected to the engine brake which incorporates a simple stop/start switch.

When the lever is released a brake block pushes against the flywheel slowing the engine down. At the same time the simple stop/start coil control switch is operated.

Check that the switch is being operated when you pull the bail lever. If not adjust the cable.

Mower on/off switch Mower plug test

Testing Bail Switch

So at this point I would go ahead and fit a new coil, because I have never fitted one of these switches.

But you can test the switch by un -plugging and checking for spark as before.

If after running the test, the plug now sparks, replace the switch.

Still no spark, go ahead, move on and replace the coil.

Mower cover Mower pull assembly Mower gas tank

Coil Replacing

Your engine may look different but this process will be the same.

Remove plastic pull assembly cover.

Remove pull assembly held on by 3 nuts.

Fuel tank is now free, take this opportunity to clean it if needed, otherwise no need to remove fuel line, just set it to the rear of the engine.

Mower coil Mower pull assembly Mower gas tank

Remove

Remove two bolts that hold the coil in place.

Remove the coil control push on wire connector, under the coil.

Mower coil Mower coil Mower coil

Fit Coil

Fit push on wire connector and bolt the coil in place, but don't tighten yet.

An air gap must be maintained between the coil and the flywheel.

A business card is just the right size. Push the coil snug against the business card and tighten the two bolts.

Remove the business card.

Rebuild in reverse order.

Don't forget to refit the push on wire connector and turn on the gas.

Nice work!

Related Questions

Brand new Honda mower won't start? The most common reason a new Honda mower won't start is because the fuel tap is turned off. The tap is positioned just below the gas cap.

 

Other possible causes include:

  • Gas level too low
  • Bail lever not pulled (if fitted)
  • Plug wire not on securely
  • Oil level too low

Honda lawn mower troubleshooting self propel? The Honda mower self propel handlebar control operates by cable and the power from the engine is transferred to the transmission with a belt.

 

Common problems are:

  • Drive belt breaks (Replace cable)
  • Drive belt jumps off (Refit cable)
  • Weak or no drive - adjust cable (Adjuster on l/h handlebar)
  • Mower hard to pull back-ways - Cable over adjusted (Adjuster on l/h handlebar)
Auto Technician and Writer at | Website

John Cunningham is an Automotive Technician and writer on Lawnmowerfixed.com. I've been a mechanic for over twenty years, I use my knowledge and experience to write "How to" articles that help fellow gear-heads with all aspects of mechanical repairs, from lawn mowers to classic cars.