Category: Lawn Mower Repair Tips

Lawn Mower Repair Tips

Lawn Mower is Blowing Out Black Smoke

If you are seeing a stream of black smoke blowing out of your exhaust pipe, your lawn mower is running in a rich condition. In other words, it is getting too much gasoline and not enough air into the engine. This makes for an excessively rich condition and will eventually foul the spark plug and carbon up the cylinder.

The first easy thing to check is the air filter to make sure that it is not clogged with dirt and grass clippings. A restricted air filter will decrease the amount of air coming into the engine and can cause this very condition.

If you have a pre-filter, it can also cause the problem. These filters can be washed and reused in many cases. Use some mild dish detergent and hot water and then wring them dry and let them sit out in the sun to dry out.

The other culprit is usually a poorly adjusted carburetor or if you are at high elevations, the wrong main jet is in the carburetor. Many carburetors today have no adjustments, but you can change out the main jet on many models of carburetors.

Look at each area of your lawn mower to determine which of these is causing the problem and correct them if needed.

Lawn Mower Repair Tips

My Lawn Mower Engine Dies After Running a Short Time

These runability problems are tricky at times to troubleshoot. Did I put good gas in the mower? Is the ignition system working properly?

Those are a couple of things that we automatically think of when our lawn mower is not working like it should. It can be frustrating to deal with those things and they must be figured out one by one.

Troubleshooting is a process of elimination. Those words alone tell so much about how to look at this problem by eliminating what it is not.

The first and easy step is to make sure there is enough gas in the tank. If that checks out fine, then move along to the next item like the ignition system. Install a spark tester and start the engine. Run it at full throttle for a while and see if at any point that the spark tends to die out. If so, there is something wrong in the ignition system. You should also change your spark plug just to eliminate that. Spark plugs are cheap so change it out.

Fuel delivery is another problem that can cause the engine to die. Is the carburetor getting the fuel it needs to run? Inspect the fuel system for blockages and such as the in tank or inline fuel filter and the carburetor itself.

By systematically eliminating these things, you will find the problem quickly. If you need professional lawn mower repair assistance, visit our Locations page for help.

Lawn Mower Repair Tips

My Lawn Mower Is Hard To Start

Lawn mowers can be finicky machines. They can be easy to start one day and hard to start the next. In most cases it is a simple adjustment to make them easier to start.

This adjustment is often a valve adjustment. Over time the valve clearance become loose and will not allow the valves to open properly. If the intake valve does not open fully, a fresh charge of gasoline will not make it into the combustion chamber. If the exhaust valve does not open fully, the hot gasses will not be expelled out the exhaust pipe and it prevents fresh gas from coming into the combustion chamber as well.

An engine is basically an air pump. Air goes in and air goes out. Whenever that cycle is interrupted, it makes it hard to start the engine. Try adjusting those valves to their proper specification and see if it makes a big difference in the starting of that engine.

You should also check to make sure that the choke is working properly. An engine choke is a butterfly type valve and you close in the carburetor. When it is closed, it creates more vacuum inside the carburetor and pulls more fuel through it and into the engine. If the choke is not closing fully, then fuel will not be adequate enough for a cold start operation.

By adjusting the choke and valves, you should have an easier starting lawn mower.

Lawn Mower Repair Tips

Lawn Mower Engine Not Getting Fuel

Depending on what kind of engine you have, there are numerous fuel delivery systems and we will go over a few here to see if you can find the problem.

On small lawn mower engine such as push and self-propelled units, the fuel is usually delivered by gravity to the carburetor. Anything that affects this gravity can cause no fuel to be delivered. Starting off the with the gas tank, you want to be sure that the fuel cap is venting properly. When you open it, is there an inrush of air? There should not be. Is the fuel strainer in the tank clogged up? Is the inline fuel filter clogged? Is there a clog in the fuel line itself?

If all of those things are fine, then that narrows things down to the carburetor. Something internally such as the needle and seat are stuck together and not letting fuel to flow.

On larger engines such as a riding lawn mower, there may be a fuel pump built into the system. As on the small engine, you want to start at the gas tank first and work your way down to the fuel pump. Then disconnect the fuel pump output side and crank the engine over. Have a catch can to catch the fuel that will squirt out.  If fuel is coming out of the fuel pump, then the logical thing is that there is a problem with the carburetor.

Loose engine intake valve clearances can also cause a lack of fuel to enter the engine. If all else fails, check those valves to ensure that they are working as they should.

Lawn Mower Repair Tips

Lawn Mower Will Run For a While and then Die

This problem can be a mystery to you and take some time to reveal what the real issue is. You are mowing along and then the engine will slowly die on you and come to a complete stop. You turn the key or pull the starter rope and it will suddenly start up and run like it normally does. What?

This happens over and over and it is puzzling to say the least. You can’t seem to find any obvious problem and the engine has good spark. So what is causing this problem?

A couple of things that cause this is the gas cap is not venting properly. As you are mowing, the gasoline level goes down and the gas must pull in air to prevent it from vacuum locking. If the vent is plugged, it will not allow air into the gas tank and thus will not let fuel into the engine or fuel injection.

You can unscrew the gas cap and if you hear an inrush of air, then you know that the cap is not venting as it should and will need replaced.

Another problem is that you can have debris that is covering the pickup tube in the gas tank or inside the carburetor float bowl. The fuel sloshing around in the carburetor bowl can cause debris to get stuck to the main jet and stop the fuel flow to the engine. After the engine dies, the debris will sink back to the bottom and when you start the lawn mower, it will run as normally.

Check these items and if you need a professional lawn mower repair shop, visit our Locations page for a shop near you.

Lawn Mower Repair Tips

Lawn Mower Leaves Grass Strips While Mowing

Leaving a grass strip can occur after maintenance or during your mowing session. If your lawn mower blades contact something such as a stump, root or rock, it can bend the lawn mower blade, the blade adapter, a deck spindle or crankshaft in the case of a push or self-propelled lawn mower.

You could also have a loose lawn mower blade and this will create vibration as well as an indication. Check all of the above items to see if they are the cause of the problem and replace any parts to correct it.

Another item that can cause this issue is that your deck is out of adjustment. If the deck was recently removed, make sure that both rear mounts are in the same holes on both sides. Also check the blade height by measuring from the ground to the tip of the blade on the outside and then measure the opposite blade. If one blade tip is higher than the other, then the deck will need to be adjusted to make sure they are both level.

The deck should also have a slight downward angle towards the front of the lawn mower. Think of how a helicopter is in flight with its blades having a downward angle to bite the air.

After you make your adjustments, test mow a section of your lawn to ensure that your changes have resolved the problem.

Lawn Mower Repair Tips, Outdoor Power Equipment Reviews, Push and Self-Propelled Lawn Mower Repair, Riding Lawn Mower Repair, Zero Turn Lawn Mower Repair

My Lawnmower Makes a Big Bang or Backfire While Mowing

You are just mowing along and your engine suddenly backfires and then it starts to continue running like normal. What could be causing this and how do I resolve it?

An engine backfire can be caused by an electrical problem or a mechanical one. In most cases it can be tracked down to an electrical problem, more specifically in the ignition system. If the ignition coil becomes too hot or has an internal breakdown, the spark will become intermittent and the combustion chamber can be ignited at the wrong time and cause a backfire out of the intake or exhaust.

The ignition kill wire could also have been compromised and partially broken because of rodent damage or heat and vibration. So you want to check it and is usually a black or gray wire that is attached to the ignition coil.

There could also be a problem with the ignition switch.

If the ignition system is working normally, then the search begins on the mechanical portion of the engine. A leak down test will need to be performed initially to determine if the intake or the exhaust valve is leaking. If one of them is leaking, the burning gasses will pass through them and cause a backfire while the engine is running and particularly under a load such as cutting the grass.

If you need a lawn mower repair shop near you to fix your mower, visit our Locations page for assistance.

Lawn Mower Repair Tips, Push and Self-Propelled Lawn Mower Repair

Push Lawn Mower Won’t Start With Fresh Gas

So you just put some fresh gas in your lawn mower and it refuses to start when you pull the cord. You pull and pull and pull and it still won’t start or it may sputter a little. But how can that be when you just put fresh gas in your lawn mower?

Well, it could be that your lawn mower sat all winter long and the gas that is in it has gone bad. The gasoline with ethanol in it today only lasts about 90 days before it starts to go bad. Once it goes bad in the carburetor, it begins to plug up the idle and main jets and then the lawn mower is not going to run at all or barely run.

A mixture of fresh and bad gas doesn’t solve the problem either. It will still cause the same non starting problem and you will be pulling until your arm wears out and have the same results. The carburetor must be removed and cleaned and all gas emptied from the system and fresh gas added before you attempt to start the lawn mower once again.

Lawn Mower Repair Tips

Lawn Mower Engine Making a Knocking Sound

Are you hearing an unusual noise coming from your lawn mowers engine? Does it sound like a knocking, banging or thumping sound?

If you have an internal engine knocking, this can be a sign of low engine oil or it could be a sign of catastrophic damage about to occur. More than likely a connecting rod is wearing out and causing it to slap against the crankshaft and eventually it will break and cause a part of it to come through the side of the crankcase.

The first thing you want to do is to check the engine oil level. If it is low, add some oil and then run the engine to warm it up. Then change that oil and look for metal particles in the old oil. If you see metal, you can be certain that your engine is wearing in an area and this will not fix itself.

At this point, the engine will need to be torn down and inspected for the cause of the problem to determine whether it is repairable or not. Some repairs on small lawn mower engine are not cost effective and a new engine or new lawn mower is the best course of action.

If you need a lawn mower repair shop in your area, visit our Locations page for assistance.

Lawn Mower Repair Tips

My Lawn Mower Has Red Gas in It

There are a couple of things that will cause your gas to look red or orange in color. One of them is someone has put fuel stabilizer in it. One particular fuel stabilizer that goes by the brand name “Stabil” is red in color while their Marine Grade is a green color. Too much Stabil added to your gasoline will cause it to look red.

If your lawn mower runs fine, then the Stabil is doing its job and keeping your gasoline stabilized. A fuel stabilizer prevents the gas from separating into different components and drying up in your carburetor bowl. This process of phase separation degrades the fuel and it begins to go bad in as little as 90 days.

If however, your lawn mower doesn’t run at all, there is a good possibility that you have off-road diesel in the tank. Off-road diesel is red in color on purpose. This is only meant for things like construction equipment and equipment that is not driven on the road, hence the name off-road.

You will need to drain all the diesel out of the lawn mower and put fresh gasoline in and the lawn mower should fun fine once again.