How To Service A Honda Petrol Lawnmower

Honda lawn mowers are designed to last a very long time.

With the correct servicing and maintenance, there is no reason a Honda lawnmower can’t last the whole lifetime of the owner.

In this article, I’m going to share all of my knowledge on how to correctly service a Honda lawnmower.

I have repaired hundreds of Honda lawnmowers and sold them for profit by simply servicing them and making them run like new again.

What I love about Honda lawnmowers the most is the great design, manoeuvrability and really easy startup process, they are really well built with high-quality cutting decks and powerful but quiet engines.

The GCC 135 and GCV 160 engines are common on many Honda lawnmowers so let’s take a look at how to service them

You can find lots more information and start repairing lawnmowers for profit by checking out my online training here

Fuel Tap And Spark Plug

Honda lawnmowers are fitted with a fuel tap which is great as it saves the need to clamp the fuel line when removing the carburettor.

Start by turning the fuel tap to the vertical position to stop the fuel flow. Next, remove the spark plug lead and completely remove the spark plug from the engine.

The correct spark plug for a Honda GCV 135 or 160 engines is NGK Spark Plug BPR6ES Suit Honda Izy Lawnmowers & Flymo XL500

The spark plug gap needs to be  0.7 to 0.8mm (0.028 to 0.032 inch)

You can find all parts required at my online parts store here

Leave the spark plug removed during all servicing and replace it after everything else is done.

Drain The Oil And Fuel

I like to use an oil extractor to drain all the oil and fuel from my lawnmowers. This eliminates the need to tip over a lawnmower while it still has oil and fuel in.

Try to avoid tipping any lawnmower with oil and fuel in as it will cause white smoke and starting problems.

I use aPela 6000 Oil Pump – Oil Extractor/Oil Extraction Kit. Oil Change Sump Pump! 6 litre . It works well and stores all the fluids until I can dispose of them in an environmentally friendly way.

It also avoids a lot of mess and is quick clean and easy. 

You can find a full playlist of Honda Lawnmower repair videos here on my Youtube channel

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Remove The Starter Recoil

With the spark plug removed and any fluids extracted the next step is to remove the starter recoil cover.

This will give you the opportunity to replace the starter rope if necessary and give much better access to the carburettor and other areas. 

To remove the starter recoil you need to remove 3 nuts on the top of the starter recoil cover, this will remove the pull start.

It is also worth removing the gas tank and the outer plastic parts from around the recoil at this point and also the air filter.

Leave the starter recoil and all covers removed until the service is complete. This will give you access to everything.

Also, make absolutely sure the spark plug is removed until all servicing is complete.

Replacing The Starter Recoil Rope

Inspect the starter recoil rope. If it looks old or frayed you should replace it. 

To replace the starter recoil rope pull out the rope as far as possible then use a clamp to hold the recoil against the spring tension. Pull out the old rope and cut it off with a knife.

Do not release the clamp at this point.

Take a new starter rope (3.5mm) is fine. Cut a length slightly longer than the rope you have removed to allow for tying some knots. Burn the end of the starter rope to stop it fraying and make the end into a point. 

Line all the holes up on the starter recoil and poke the new rope back through. It’s easier to push back through when the end us burned. Tie a knot and pull it tight.

Again. Do not release the clamp.

Burn the opposite end of the pull cord and attach a new starter handle.

Slowly release the clamp and allow the spring tension to wind up the starter rope slowly.  

Take a look at this video for a demonstration.

Cooling Fins

With the starter, recoil and any plastic housing removed be sure to blow out any debris from the cooling fins. This is an ideal time to do it before you remove the carburettor for servicing.

If you have a lawnmower that starts then dies after a minute or so when it gets hot, it’s usually because the cooling fins are blocked causing the engine to overheat.

How To Service The Carburettor On A Honda Lawnmower

The first time you service a lawnmower carburettor it can seem a little tricky and awkward. With a little practice, you can have this job done in around 10 minutes. 

There is a step by step detailed video of this available on my Honda repair manual DVD

With the air filter removed you will see 3 bolts that run through the air filter box housing. Remove these 3 bolts and set aside the air filter housing.

The carburettor will drop down at this point which is perfectly normal.

I strongly suggest taking a few photos of all springs any linkages that connect to the carburettor at this point!

Next, you will need to unhook the two governor linkages and a spring from the top of the carburettor. This can be made easier by loosening the bolt in the centre of the control arm. 

Pull the fuel line off the carburettor and remove it from the lawnmower.

Take a small tub and place the carburettor inside it, this will help collect any fuel left in the carburettor and keep all the parts together.

Tip the carburettor over and drain out any excess fuel. Next, remove the bolt from the bottom of the carburettor with a 10mm spanner or socket and take off the bowl.

Be sure to keep an eye on the gasket the sits between the bowl and the carburettor. If it’s broken or worn replace it.

You will now see the float and a retaining pin. Turn the carburettor upside down and pull out the retaining pin. Carefully remove the float and watch for the small needle dropping out.

Do not lose this part!

Now you need to remove the main jet. Take a thin flathead screwdriver and undo the main jet from the underside. Undo the screw until the jet drops out. There is no setting involved so simply remove it.

If the jet does not drop out take a small Allen key and push it down from the top. You will now see the jet is in 2 pieces, a short and a long piece.

Clean all the tiny holes out using carburettor spray and compressed air. If any of these holes are blocked then your lawnmower will either not start or not idle properly.

Take some carburettor cleaning spray and clean the rest of the carburettor making sure every tiny hole is clean.

Be sure to remove any screws and also spray inside these areas with carburettor spray. Blow everything through with compressed air and make sure everything is dry.

If you have an ultrasonic cleaner then I advise using it as this removes any dirt from parts we could not otherwise access.

Replace any screws then insert the longer thin part of the main jet back into the carburettor. The thin end drops in first, then re-insert the other smaller part and re-tighten using a small flathead screwdriver.

Make absolutely sure every part is clean including the bowl and needle.

Replace the needle on the float bowl and insert back into place, then re-fit the retaining pin

Replace the bowl and hand tighten the bowl bolt.

These bolts are very easy to cross-thread so take extra care to tighten by hand, then finally tighten with a spanner.

Before reconnecting the carburettor linkages back on the carburettor hook up the fuel line and turn on the fuel tap while holding the carburettor in position. Check for any leaks from the carburettor.

If it does leak it is highly likely the needle isn’t seated correctly and the float isn’t operating properly.

If everything looks fine then turn off the fuel tap and leave the fuel line connected. It is much more difficult to reconnect the fuel line once the air filter box is back in position.

Take a look at this video where I show how to service the carburettor on a Honda petrol lawnmower

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Refit The Carburettor

To refit the carburettor back on a Honda lawnmower make sure the fuel line is connected then connect the spring to the furthest hole and the longer linkage to the nearer hole on the carburettor.

There is one more smaller linkage the connects to the near side of the carburettor.

Offer the carburettor up to the lawnmower engine and line up all the gaskets and holes. Take the air filter box and one long screw and insert the screw through the air filter box, through the carburettor gaskets and spacers and lightly tighten into the engine.

Take the second bolt and repeat the process. Evenly tighten the bolts and remember to re-insert the rubber breather pipe to the back of the air filter box.

This is the most difficult part so be patient and get someone to help you hold everything if necessary.

Fit a new air filter if required then the servicing of your Honda lawnmower carburettor will be complete.

Replace The Air Filter

After servicing the carburettor be sure to replace the air filter. They are cheap to replace. If you do not wish to replace it be sure to blow any dirt out of the old filter using compressed air.

You don’t want dirt entering the carburettor at any point especially when you have gone to the trouble of cleaning it.

How To Adjust The Valves On A Honda Lawnmower.

If you have a Honda lawnmower that’s difficult to pull over or doesn’t run evenly especially on lower speeds there is a very good chance the valves need adjusting.

I strongly advise servicing the carburettor to resolve any poor running issues before adjusting the valves as this eliminates 90% of hunting and surging issues.

Honda lawnmowers are renowned for there easy starting and the pull cord she be almost effortless and smooth when pulled.

Adjusting the valves makes a massive difference to how easy it is to pull over and start a Honda petrol lawnmower.

Honda GCV 135 and 160 engines both have an overhead valve set up (OHV) that is designed to be adjusted.

Remove the overhead valve cover carefully by removing the surrounding bolts and gently lifting off the cover. Try not to disturb the gasket sealant.

You will now see the valve and the valve stems.

Remove the spark plug and place a plastic screwdriver down the spark plug hole and feel for the piston. Turn the starter to move the piston towards you until you find top dead centre (TDC).

At this point, you should have one valve all the way open and one valve fully closed.

Take a feeler gauge and slide it between the open valve stem and valve.

The correct clearance for the inlet valve is 0.006 inch +/- 0.016 inches.

The correct clearance for the exhaust valve is 0.008 inches +/- 0.002 inch.

To see a detailed video on how to adjust the valves take a look here on my youtube channel and follow the tutorial.

Please feel free to subscribe to my channel.

In simple terms, it’s a case of loosening the locking nut and adjusting the clearance using the adjuster.

One tip is to keep a spanner on the locking nut whilst doing the adjustment and take care locking back up.

Once the correct clearance is achieved it will be much easier to pull over and start the lawnmower and it will run much more evenly if the carburettor has been serviced.

Many times the valves need tightening as the clearance is too large causing lack of compression when attempting to start.

Replace the overhead valve cover using gasket sealant if required.

You can often get a feel for the valves been set by manually turning the flywheel. It should feel more even with a good amount of resistance.

This process is very similar on all overhead valve lawnmowers so it’s well worth the time learning how to do this procedure.

Setting The Ignition Coil

It shouldn’t be necessary to adjust the air gap between the ignition coil and the flywheel, however, I pick up all sorts of lawnmowers where someone has had a play around and loosened parts unnecessarily.

The correct air gap between the ignition coil and flywheel on a Honda GCV 135 or GCV 160 engine is 0.254mm to 0.355 mm or 0.010 inches to 0.002 inch.

Generally, I use an old greetings card to set the gap and I know many people use a playing card!

To set the ignition coil gap turn the flywheel so the magnets are facing away from the ignition coil. Back off both bolts holding the ignition coil in place.

Next, take an old greetings card or something of similar thickness and place it in the gap between the ignition coil and the flywheel.

Turn the flywheel until the magnets pick up the coil and are separated only by the card.

Lock up the two bolts and turn the flywheel to remove the card.

This is an easy way to set an even gap between the ignition coil and the flywheel.

I use this method regularly and never have a problem.

How To Remove A Honda Lawnmower Blade

With the spark plug removed and the fuel and oil extracted tip the lawnmower with the carburettor facing up and the exhaust facing down towards the floor.

Lean the lawnmower against a wall or fence so you can access the underside.

Use a 13 mm socket and undo the two bolts that hold the blade in place and remove the blade.

I suggest taking the blade to a machine shop for sharpening for best results.

If you wish to sharpen the blade yourself you can simply use a file to follow the natural angle of the cutting edge or use a bench grinder.

I recommend using a blade balancing tool to ensure the blade is evenly weighted too.

One thing to remember is that the correct angle is needed to provide the correct back lift for the cut grass to be transferred correctly to the grass box and if the blade isn’t balanced evenly you will experience more vibration throughout the lawnmower when cutting.

For these reasons, it’s often better to use a local lawnmower repair shop or replace the blade.

Check The Self Drive Belt.

With the blade removed it is advisable to remove the belt guard and clear out any debris. I recently picked up a lawnmower where the self-drive didn’t work because debris had built up in the belt guard and dragged the belt off!

Most times when this happens the drive belt gets chopped to pieces by the blade so it’s well worth taking the time to do this part of the service with the blade removed.

Check the belt for signs of wear at this point.

Clean The Cutting Deck

I have seen so many lawnmowers with perfectly running engines and rotten decks.

This is one of the main reasons people scrap or sell their lawnmowers.

To avoid this take a wire brush, scraper or pressure washer and remove any build up of grass from the underside of the cutting deck. If possible take the time to paint the underside of the deck.

I usually use Hammerite black paint.

Doing this with the blade removed is very quick and easy to do and will massively extend the life of the cutting deck.

Also, avoid where possible cutting wet or damp grass. If your lawnmower has a self-cleaning cutting deck feature be sure to make use of it.

Check The Microswitch

Most Honda lawnmowers use a micro switch instead of a kill switch.

The microswitch must be activated to allow the ignition coil to work and in turn, cause the spark plug to.. well… spark!

Pull the safety lever of the lawnmower with the starter recoil removed and you will see the switch being activated.

Make sure it moves freely and is unobstructed. Occasionally I have seen the lever not moving far enough to activate the microswitch properly.

You can see a demonstration on this video.

How To Set The Automatic Choke On A Honda Lawnmower

Honda lawnmowers use an automatic choking mechanism which eliminates the need to manually prime the engine.

One of the main reasons Honda lawnmowers occasionally become difficult to start is because the automatic choke mechanism isn’t functioning correctly.

To service the choke mechanism remove the air filter cover and air filter.

Get a friend or handy helper to operate the throttle lever and take a look through the inner air filter box into the carburettor.

You will see a small valve which I refer to as a gold butterfly choke.

With the throttle set to choke this valve should be fully closed to enable the engine to choke efficiently.

With the throttle set to full speed, the butterfly should be fully open allowing maximum airflow.

The choke is set by the position of the throttle cable.

Follow the throttle cable from the handle down to the control arm on the lawnmower to locate the correct cable.

Back off the screw that holds the cable and set the throttle to choke.

Manually move the cable until the butterfly choke is fully closed then tighten the cable up in that position.

Check that the choke opens and closes correctly by operating the throttle lever and watching the butterfly open and close correctly.

Having a poorly adjusted choke or a micro switch that fails to operate are the 2 main reasons I regularly come across that stop a Honda lawnmower from starting up.

Technical Data For Honda GCV Engines

  • Spark Plug Type NGK BPR6ES
  • Spark Plug Gap 0.7 to 0.8 mm (0.028 0.032 inches)
  • Valve Clearances Intake 0.15 mm +/- 0.04 mm (0.006 +/- 0.016 inch)
  • Exhaust Clearance 0.20 +/- 0.04mm ( 0.008 +/- 0.002 in)
  • Ignition Coil Armature Air Gap 0.254 to 0.355 mm (0.010 to 0.002 inch)
  • Engine Oil Grade 10W-40
  • Engine Oil Capacity 0.55 litres.
  • Torque Wrench Settings
  • Big End Bolts 12 Nm
  • Flywheel Nut 52 Nm

Checking The Flywheel Key

If you have lawnmower kickback problems after all servicing is complete you will need to check the flywheel key.

If a flywheel key is even slightly damaged it massively changes the timing of the lawnmower.

Remove the starter recoil covers and you will see the flywheel.

Use a flywheel puller to pull the flywheel from the crankshaft and inspect the flywheel key.

It should be a perfect shape.

If there are any knocks or imperfections replace the keyway.

Take a look at this video for a demonstration

The flywheel key sets the position of the flywheel on the crankshaft and the timing of the spark.

If the flywheel is slightly damaged you will get an incorrectly timed lawnmower with the spark plug sparking at the wrong time causing vibration and starting problems.

You can read more about lawnmower kickback problems here

Purchasing Spare Honda Lawnmower Parts.

Many parts are available from the recommended products section of this website.

Beware of after market parts particularly carburettors and started recoils. In my experience it never pays to use after market parts as they tend to cause more problems in the long run.

Service Sticker

To find the correct parts for your lawnmower you will need to find the service sticker.

This is usually a silver sticker located either on the side of the cutting deck or on the top of the cutting deck.

These are the details your local lawnmower service centre will need to source the correct parts for your lawnmower or if you are looking to buy spare parts online.

I suggest taking a photograph on a mobile phone to keep a record of this using the free google photos app to keep a backup.

This way you will always have access to the information as long as you usually carry a mobile phone.

Service stickers tend to get damaged with fuel and fade over time and without this information, it can often be difficult to locate correct spare parts

Final Thoughts

Honda lawnmowers can last a very long time with the correct service and maintenance. You can read more about why in this article

You can find lots more information and start repairing lawnmowers for profit by checking out my online training here

Here are a couple of useful videos on Honda Lawnmower repair.

There are many reasons I recommend Honda lawnmowers in many of my articles, the main reasons are because they are incredibly easy to start when set up correctly, very easy to manoeuvre have super solid cutting decks and reliable powerful yet quiet engines.

Honda throttles work well and the roto stop clutch feature is a must when cutting larger areas as it saves having to re-start the mower after emptying the grass bag.

Be sure to check out my recommended products page for a full list of all lawnmowers I’m happy to recommend.

The handles on Honda Lawnmowers attach to the cutting deck sensibly and are designed to last.

My personal favourite is The Honda IZY range of lawnmowers fitted with the GCV 135 and 160 engines. Take a look at the design here Honda Izy HRG 416 SK Petrol Self Propelled Rotary Lawnmower – 4 Wheeled

I have picked up plenty of Honda lawnmowers to repair for profit and the Honda IZY range always runs like new again after a good service.

The clever design of the cutting deck and wheels combined with the handle set up makes these lawnmowers very easy to use and they produce an excellent finish.

Spare parts are widely available and sensibly priced. I have recently included the Honda IZY range of lawnmower in my list of lawnmowers that could potentially last a lifetime in my article

Be sure to check out all my free Honda lawnmower repair videos available here on my youtube channel.

Please feel free to subscribe to my channel on Youtube it’s free!

You can find lots more information and start repairing lawnmowers for profit by checking out my online training here

I hope this article helps with the servicing of your Honda Lawnmower. Feel free to look in the recommended products section of this website for any service parts you may need.

Happy Mowing.










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