Concrete Saw: Won't Start
If your concrete saw won't start, this can be extremely frustrating. Luckily, this can be fixed rather quickly. Review the parts below to determine which one is likely the cause. Our in-house repair technicians have put together a guide to help you conduct this repair on your own. Much more satisfying than getting someone else to fix it. Refer to your owner's manual for more detailed instructions.
Armatures
The armature is the rotating part of an electric motor, which consists of wires wound around two or more poles of an iron core. The armature has a commutator, located on its shaft, where brushes ride on. The commutator acts as a switch for the electromagnet, constantly flipping the flow of electrons at the exact moment, causing the armature to rotate.
First, remove the end cap for the motor and remove the carbon brushes with a screwdriver. Set aside. Continue removing the cover to access the motor by removing the screws on the cover. Separate the covers. Once you have reached the armature, pull it out.
To check for a bad armature, you can perform the 180-degree test. With the armature removed from the unit, stand it up on a bench. With an ohmmeter, attach the two ends to both sides of the commutator to measure the resistance of the...
First, remove the end cap for the motor and remove the carbon brushes with a screwdriver. Set aside. Continue removing the cover to access the motor by removing the screws on the cover. Separate the covers. Once you have reached the armature, pull it out.
To check for a bad armature, you can perform the 180-degree test. With the armature removed from the unit, stand it up on a bench. With an ohmmeter, attach the two ends to both sides of the commutator to measure the resistance of the...
The armature is the rotating part of an electric motor, which consists of wires wound around two or more poles of an iron core. The armature has a commutator, located on its shaft, where brushes ride on. The commutator acts as a switch for the electromagnet, constantly flipping the flow of electrons at the exact moment, causing the armature to rotate.
First, remove the end cap for the motor and remove the carbon brushes with a screwdriver. Set aside. Continue removing the cover to access the motor by removing the screws on the cover. Separate the covers. Once you have reached the armature, pull it out.
To check for a bad armature, you can perform the 180-degree test. With the armature removed from the unit, stand it up on a bench. With an ohmmeter, attach the two ends to both sides of the commutator to measure the resistance of the windings. As you move it around the commutator, the reading number is not important. You are looking for a consistent reading, indicating all the windings are good. If it varies radically, reading a zero or open circuit, then the armature is not good.
Another test can be done by attaching the ohmmeter on each bar, adjacent to each other on the commutator. Again, look for a consistent reading. If the ohm reads zero or open circuit, that indicates a bad armature. The final test is the bar to ground test. This is done by placing one end of the ohmmeter to the tip of the shaft on the armature and the other to the commutator. If the armature is bad, install a new one. Once completed, reinstall the covers, brushes and the end cap of the motor.
First, remove the end cap for the motor and remove the carbon brushes with a screwdriver. Set aside. Continue removing the cover to access the motor by removing the screws on the cover. Separate the covers. Once you have reached the armature, pull it out.
To check for a bad armature, you can perform the 180-degree test. With the armature removed from the unit, stand it up on a bench. With an ohmmeter, attach the two ends to both sides of the commutator to measure the resistance of the windings. As you move it around the commutator, the reading number is not important. You are looking for a consistent reading, indicating all the windings are good. If it varies radically, reading a zero or open circuit, then the armature is not good.
Another test can be done by attaching the ohmmeter on each bar, adjacent to each other on the commutator. Again, look for a consistent reading. If the ohm reads zero or open circuit, that indicates a bad armature. The final test is the bar to ground test. This is done by placing one end of the ohmmeter to the tip of the shaft on the armature and the other to the commutator. If the armature is bad, install a new one. Once completed, reinstall the covers, brushes and the end cap of the motor.
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Fields
See field testing under armature.
See field testing under armature.
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Power Cords
The cord supplies power to the saw. To check and replace the cord, separate the handle where the cord enters the saw by removing the screws. Remove the cord at the terminals on the switch and pull the cord out. To test the cord, twist the ends together and attach and ohmmeter to the plug portion of the cord and check continuity. Set the ohmmeter to the lowest setting. If the reading is close to zero, the cord is good. If it reads infinity, the cord is bad and needs to be replaced. Install a new cord by attaching the ends to the terminals on the switch and reattach the two parts of the handle back together.
The cord supplies power to the saw. To check and replace the cord, separate the handle where the cord enters the saw by removing the screws. Remove the cord at the terminals on the switch and pull the cord out. To test the cord, twist the ends together and attach and ohmmeter to the plug portion of the cord and check continuity. Set the ohmmeter to the lowest setting. If the reading is close to zero, the cord is good. If it reads infinity, the cord is bad and needs to be replaced. Install a new cord by attaching the ends to the terminals on the switch and reattach the two parts of the handle back together.
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Switches
The on/off switch allows the flow of electricity to the electric motor, or if it is gas powered at the ignition. If this switch is malfunctioning, you can test and replace if necessary. You will need to gain access to this switch. This will be different on all models, as there are many different saws on the market – some being gas, electric, walk behind and tabletop. Determine what you will need to access this switch. For most models, it is just a matter of separating the two halves of the handle or removing the cover. Once you have accessed the switch, inspect that the wires are properly attached and tight. Remove the switch and hook up and ohmmeter. Select the ohmmeter to the lowest reading. With the switch in the on position, it should ready zero, or very close to zero. In the off position, it should ready infinity....
The on/off switch allows the flow of electricity to the electric motor, or if it is gas powered at the ignition. If this switch is malfunctioning, you can test and replace if necessary. You will need to gain access to this switch. This will be different on all models, as there are many different saws on the market – some being gas, electric, walk behind and tabletop. Determine what you will need to access this switch. For most models, it is just a matter of separating the two halves of the handle or removing the cover. Once you have accessed the switch, inspect that the wires are properly attached and tight. Remove the switch and hook up and ohmmeter. Select the ohmmeter to the lowest reading. With the switch in the on position, it should ready zero, or very close to zero. In the off position, it should ready infinity. If this is not happening, then you require a new switch. Install a new switch if needed and reassemble your saw back together.
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Air Filters
The air filter filters out all contaminants from entering the engine, causing internal problems with the carburetor as well as internal engine damage. A heavily-clogged air filter will prevent the flow of air into the engine for combustion, causing a no-start situation. Check the air filter and replace it regularly. This type of saw creates a lot of dust and debris, therefore the air filter requires more attention. Concrete saws tend to have a pre-filter; you can take it out and wash it regularly under water.
The air filter filters out all contaminants from entering the engine, causing internal problems with the carburetor as well as internal engine damage. A heavily-clogged air filter will prevent the flow of air into the engine for combustion, causing a no-start situation. Check the air filter and replace it regularly. This type of saw creates a lot of dust and debris, therefore the air filter requires more attention. Concrete saws tend to have a pre-filter; you can take it out and wash it regularly under water.
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Fuel Filters
The fuel filters out all contaminants from entering the engine, causing damage. Concrete saws can cause a lot of dust so therefore filters should be checked and replaced more often. Remove the gas cap and use a hook to insert it in the fuel tank and pull the fuel line up. The filter is attached to the end of this line. Pull the filter off and replace. Then, feed it back in the tank. Reinstall the gas cap.
The fuel filters out all contaminants from entering the engine, causing damage. Concrete saws can cause a lot of dust so therefore filters should be checked and replaced more often. Remove the gas cap and use a hook to insert it in the fuel tank and pull the fuel line up. The filter is attached to the end of this line. Pull the filter off and replace. Then, feed it back in the tank. Reinstall the gas cap.
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Gaskets
The gasket between the carburetor and intake prevents excess air from entering the engine under operating conditions. This causes a lean fuel mixture that impacts the engine’s performance. If this gasket is in really poor shape, it can cause the engine not to start, as the vacuum created by the engine will pull excess air into the engine.
Remove the top cover and disconnect the linkage for the butterfly valve, located on this cover. Next, take out the air filter, pre-filter, and filter. Take off the mounting plate for the air filter housing. Remove any carburetor linkage. This will vary on models but are similar to other carburetor linkages. Disconnect any fuel lines (if you have to) and pull the carburetor off.
Check and replace the gasket, or seal, in between the carburetor and intake. Clean the area with carburetor cleaner before installing a new gasket or seal. Reinstall the...
Remove the top cover and disconnect the linkage for the butterfly valve, located on this cover. Next, take out the air filter, pre-filter, and filter. Take off the mounting plate for the air filter housing. Remove any carburetor linkage. This will vary on models but are similar to other carburetor linkages. Disconnect any fuel lines (if you have to) and pull the carburetor off.
Check and replace the gasket, or seal, in between the carburetor and intake. Clean the area with carburetor cleaner before installing a new gasket or seal. Reinstall the...
The gasket between the carburetor and intake prevents excess air from entering the engine under operating conditions. This causes a lean fuel mixture that impacts the engine’s performance. If this gasket is in really poor shape, it can cause the engine not to start, as the vacuum created by the engine will pull excess air into the engine.
Remove the top cover and disconnect the linkage for the butterfly valve, located on this cover. Next, take out the air filter, pre-filter, and filter. Take off the mounting plate for the air filter housing. Remove any carburetor linkage. This will vary on models but are similar to other carburetor linkages. Disconnect any fuel lines (if you have to) and pull the carburetor off.
Check and replace the gasket, or seal, in between the carburetor and intake. Clean the area with carburetor cleaner before installing a new gasket or seal. Reinstall the carburetor and hook up the fuel line and linkages. Replace the top gasket between the carburetor and mounting plate for the air cleaner assembly. Reinstall the mounting place for the air filter.
At this time, check the air filter and replace if needed and reinstall. Clean the pre-filter and reinstall. Put the top cover back on and reconnect the linkage to the butterfly valve. Secure the top cover back down.
Remove the top cover and disconnect the linkage for the butterfly valve, located on this cover. Next, take out the air filter, pre-filter, and filter. Take off the mounting plate for the air filter housing. Remove any carburetor linkage. This will vary on models but are similar to other carburetor linkages. Disconnect any fuel lines (if you have to) and pull the carburetor off.
Check and replace the gasket, or seal, in between the carburetor and intake. Clean the area with carburetor cleaner before installing a new gasket or seal. Reinstall the carburetor and hook up the fuel line and linkages. Replace the top gasket between the carburetor and mounting plate for the air cleaner assembly. Reinstall the mounting place for the air filter.
At this time, check the air filter and replace if needed and reinstall. Clean the pre-filter and reinstall. Put the top cover back on and reconnect the linkage to the butterfly valve. Secure the top cover back down.
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Pistons
Piston rings create the seal between the piston and cylinder walls for compression in the combustion chamber. If these rings wear out, the pressure in the combustion chamber will drop, causing the engine to lose significant power and not perform.
To check the piston rings, start by doing a compression test with a compression test gauge. To do so, remove the spark plug and attach the compression gauge and turn the engine over. Check your gauge. Refer to your owner’s manual, or repair manual, for the specifications for your model. Write down the number from the test and compare that to what the manufacturer’s specifications are. If there is a big difference that is a good indication the rings are bad.
To confirm, add a little oil inside the cylinder. Oil will take up space between the rings and the wall. Turn the engine over for a second time and...
To check the piston rings, start by doing a compression test with a compression test gauge. To do so, remove the spark plug and attach the compression gauge and turn the engine over. Check your gauge. Refer to your owner’s manual, or repair manual, for the specifications for your model. Write down the number from the test and compare that to what the manufacturer’s specifications are. If there is a big difference that is a good indication the rings are bad.
To confirm, add a little oil inside the cylinder. Oil will take up space between the rings and the wall. Turn the engine over for a second time and...
Piston rings create the seal between the piston and cylinder walls for compression in the combustion chamber. If these rings wear out, the pressure in the combustion chamber will drop, causing the engine to lose significant power and not perform.
To check the piston rings, start by doing a compression test with a compression test gauge. To do so, remove the spark plug and attach the compression gauge and turn the engine over. Check your gauge. Refer to your owner’s manual, or repair manual, for the specifications for your model. Write down the number from the test and compare that to what the manufacturer’s specifications are. If there is a big difference that is a good indication the rings are bad.
To confirm, add a little oil inside the cylinder. Oil will take up space between the rings and the wall. Turn the engine over for a second time and take a reading. If the reading goes up, your rings are bad and need to be replaced.
To replace, you will have to tear down the engine. Start by removing the recoil. Take off the belt cover and release the tension on the belt. Turn the saw on its side and disconnect the water line. Remove the belt from the pulley and the blade. Take out the muffler and inspect the piston and rings for damage by looking through the exhaust port. Remove the top cover and disconnect the linkage for the butterfly valve on this cover. Take the handle off and then the spark plug wires. Move the switch wires out of the way. Remove the cover over the engine as well as the side cover. Take off the bottom crankcase bolts. Disconnect the intake boot from the cylinder by loosening the clamp on the boot, removing the clamp. Next, with a dull-flathead screwdriver, pry the boot off gently.
At this point, you can now remove the cylinder head sleeve by twisting it back and forth, pulling upwards. With a small flat-blade screwdriver, remove the piston rings. Install the new piston rings by pushing them over the piston, positioning the ring gaps 1/3 away from each other to prevent blow by. Apply clean engine oil to the cylinder head sleeve and reinstall it over the piston. These parts are small enough that you can just use your hands to push the rings together to get them in the cylinder. Once reinstalled, fasten it back down. Reinstall the boot and clamp and tighten the clamp down. Reinstall the bottom crankcase bolts and tighten to the manufacturer’s specifications. Reinstall the top and side covers. Reattach the spark plug wires as well as the switch wires. Put the handle on and reinstall the outer top cover, reconnecting the linkage for the butterfly valve. Connect the muffler. Install the belt around the pulley and install the blade. Reapply the tension and put the water line back in. Install the belt cover and then the recoil.
To check the piston rings, start by doing a compression test with a compression test gauge. To do so, remove the spark plug and attach the compression gauge and turn the engine over. Check your gauge. Refer to your owner’s manual, or repair manual, for the specifications for your model. Write down the number from the test and compare that to what the manufacturer’s specifications are. If there is a big difference that is a good indication the rings are bad.
To confirm, add a little oil inside the cylinder. Oil will take up space between the rings and the wall. Turn the engine over for a second time and take a reading. If the reading goes up, your rings are bad and need to be replaced.
To replace, you will have to tear down the engine. Start by removing the recoil. Take off the belt cover and release the tension on the belt. Turn the saw on its side and disconnect the water line. Remove the belt from the pulley and the blade. Take out the muffler and inspect the piston and rings for damage by looking through the exhaust port. Remove the top cover and disconnect the linkage for the butterfly valve on this cover. Take the handle off and then the spark plug wires. Move the switch wires out of the way. Remove the cover over the engine as well as the side cover. Take off the bottom crankcase bolts. Disconnect the intake boot from the cylinder by loosening the clamp on the boot, removing the clamp. Next, with a dull-flathead screwdriver, pry the boot off gently.
At this point, you can now remove the cylinder head sleeve by twisting it back and forth, pulling upwards. With a small flat-blade screwdriver, remove the piston rings. Install the new piston rings by pushing them over the piston, positioning the ring gaps 1/3 away from each other to prevent blow by. Apply clean engine oil to the cylinder head sleeve and reinstall it over the piston. These parts are small enough that you can just use your hands to push the rings together to get them in the cylinder. Once reinstalled, fasten it back down. Reinstall the boot and clamp and tighten the clamp down. Reinstall the bottom crankcase bolts and tighten to the manufacturer’s specifications. Reinstall the top and side covers. Reattach the spark plug wires as well as the switch wires. Put the handle on and reinstall the outer top cover, reconnecting the linkage for the butterfly valve. Connect the muffler. Install the belt around the pulley and install the blade. Reapply the tension and put the water line back in. Install the belt cover and then the recoil.
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Spark Plugs
The spark plug produces the spark to ignite the air/fuel mixture inside the combustion chamber. To check the condition of the spark plug, remove the spark plug boot and remove the spark plug. Inspect the spark plug – it should be light grey or brown for normal conditions. You can clean, re-gap and use this plug again but it is always best to replace, as they are an inexpensive maintenance part and should be changed regularly. If the plug has deposits, corrosion, melting, eroding, or wet fouling, the plug must be replaced. The engine should be repaired from what is causing the issue of the malfunctioning plug.
The spark plug produces the spark to ignite the air/fuel mixture inside the combustion chamber. To check the condition of the spark plug, remove the spark plug boot and remove the spark plug. Inspect the spark plug – it should be light grey or brown for normal conditions. You can clean, re-gap and use this plug again but it is always best to replace, as they are an inexpensive maintenance part and should be changed regularly. If the plug has deposits, corrosion, melting, eroding, or wet fouling, the plug must be replaced. The engine should be repaired from what is causing the issue of the malfunctioning plug.
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Brushes
The brushes provide the electrical current to the armature by riding on the commutator. If these brushes become damage in any way, it can impact their ability to provide the electrical current. Remove the motor end cap and locate the brush caps. Using a screwdriver, take off the brush caps and then remove the brush from the motor. If the brush is damaged from overheating, you may need to use a small screwdriver and pliers to pull out and break what is left of the carbon brush. Clean out the inside and insert the new brush by aligning the wings on the end of the brush with the holder. Hold the brush in place and reinstall the cap. Do not over tighten the cap as it can break easily.
The brushes provide the electrical current to the armature by riding on the commutator. If these brushes become damage in any way, it can impact their ability to provide the electrical current. Remove the motor end cap and locate the brush caps. Using a screwdriver, take off the brush caps and then remove the brush from the motor. If the brush is damaged from overheating, you may need to use a small screwdriver and pliers to pull out and break what is left of the carbon brush. Clean out the inside and insert the new brush by aligning the wings on the end of the brush with the holder. Hold the brush in place and reinstall the cap. Do not over tighten the cap as it can break easily.
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Coils
The coil produces the electrical current for the spark plug. Remove the side cover and locate the ignition coil beside the flywheel. Remove the bolts holding it in place. Take out the wire and then the spark plug by turning the coil counter clockwise, pulling the wire off. Install the spark plug wire back on the coil and turn clockwise until tight. Reattach the other wire. Reinstall the coil on the engine with bolts hand tight. Place a business card between the flywheel and the coil then spin the flywheel around so the magnets on the flywheel are facing the coil. Let the magnets pull the coil in place and tighten the bolts. Remove the business card and reinstall the side cover.
The coil produces the electrical current for the spark plug. Remove the side cover and locate the ignition coil beside the flywheel. Remove the bolts holding it in place. Take out the wire and then the spark plug by turning the coil counter clockwise, pulling the wire off. Install the spark plug wire back on the coil and turn clockwise until tight. Reattach the other wire. Reinstall the coil on the engine with bolts hand tight. Place a business card between the flywheel and the coil then spin the flywheel around so the magnets on the flywheel are facing the coil. Let the magnets pull the coil in place and tighten the bolts. Remove the business card and reinstall the side cover.
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Carb Kits
The carburetor is designed to mix fuel and air in the proper ration for a clean combustion. Over time, especially in two-stroke engines, carburetors tend to become gummed up inside and require a rebuild to restore them to new condition.
To do this, remove the top cover and disconnect the linkage for the butterfly valve on this cover. Next, remove the air filter cover, pre-filter, and filter. Remove the mounting plate for the filter housing. Remove the carburetor linkage. This will vary on models but is like any other carburetor linkage. Disconnect any fuel lines. Remove the carburetor. Clear any screws on the cover of the carburetor and pull the diaphragm and gasket out. Remove the cover on the fuel flap side and remove the gasket. Use a small flat-tip screwdriver to take out fuel screen.
Now, install the new screen evenly. Remove the needle valve, arm, spring, and pin....
To do this, remove the top cover and disconnect the linkage for the butterfly valve on this cover. Next, remove the air filter cover, pre-filter, and filter. Remove the mounting plate for the filter housing. Remove the carburetor linkage. This will vary on models but is like any other carburetor linkage. Disconnect any fuel lines. Remove the carburetor. Clear any screws on the cover of the carburetor and pull the diaphragm and gasket out. Remove the cover on the fuel flap side and remove the gasket. Use a small flat-tip screwdriver to take out fuel screen.
Now, install the new screen evenly. Remove the needle valve, arm, spring, and pin....
The carburetor is designed to mix fuel and air in the proper ration for a clean combustion. Over time, especially in two-stroke engines, carburetors tend to become gummed up inside and require a rebuild to restore them to new condition.
To do this, remove the top cover and disconnect the linkage for the butterfly valve on this cover. Next, remove the air filter cover, pre-filter, and filter. Remove the mounting plate for the filter housing. Remove the carburetor linkage. This will vary on models but is like any other carburetor linkage. Disconnect any fuel lines. Remove the carburetor. Clear any screws on the cover of the carburetor and pull the diaphragm and gasket out. Remove the cover on the fuel flap side and remove the gasket. Use a small flat-tip screwdriver to take out fuel screen.
Now, install the new screen evenly. Remove the needle valve, arm, spring, and pin. Remove the adjusting screw and inspect the needle valve at the end. It should have a tip and should not be mushroomed. Use the carburetor cleaner to spray the entire carburetor and clean with a cloth. Dry the carburetor thoroughly, with compressed air, if possible.
First, install the new needle valve spring then the arm pin and arm with the needle valve together. Hold down as you fasten it tight. Install the gasket and diaphragm, with the ring side down, and reinstall the cover. Tighten down. On the fuel flap side, install the new flap and line it up properly. Then, install the gasket and tighten down the cover. Reinstall the adjusting needle, very gently, until it bottoms out then turn it back 1 1/14 to 1 1/8 turn. Put in the carburetor by hooking the fuel lines back up, along with the linkages and replace the gasket, or seal, under the carburetor to the intake.
Replace the top gasket between the carburetor and mounting plate for the air cleaner assembly. Reinstall the mounting plate for the air filter and reinstall the air filter assembly. Finally, put the top cover back on and reconnect the linkage to the butterfly valve. Secure the top cover back down.
To do this, remove the top cover and disconnect the linkage for the butterfly valve on this cover. Next, remove the air filter cover, pre-filter, and filter. Remove the mounting plate for the filter housing. Remove the carburetor linkage. This will vary on models but is like any other carburetor linkage. Disconnect any fuel lines. Remove the carburetor. Clear any screws on the cover of the carburetor and pull the diaphragm and gasket out. Remove the cover on the fuel flap side and remove the gasket. Use a small flat-tip screwdriver to take out fuel screen.
Now, install the new screen evenly. Remove the needle valve, arm, spring, and pin. Remove the adjusting screw and inspect the needle valve at the end. It should have a tip and should not be mushroomed. Use the carburetor cleaner to spray the entire carburetor and clean with a cloth. Dry the carburetor thoroughly, with compressed air, if possible.
First, install the new needle valve spring then the arm pin and arm with the needle valve together. Hold down as you fasten it tight. Install the gasket and diaphragm, with the ring side down, and reinstall the cover. Tighten down. On the fuel flap side, install the new flap and line it up properly. Then, install the gasket and tighten down the cover. Reinstall the adjusting needle, very gently, until it bottoms out then turn it back 1 1/14 to 1 1/8 turn. Put in the carburetor by hooking the fuel lines back up, along with the linkages and replace the gasket, or seal, under the carburetor to the intake.
Replace the top gasket between the carburetor and mounting plate for the air cleaner assembly. Reinstall the mounting plate for the air filter and reinstall the air filter assembly. Finally, put the top cover back on and reconnect the linkage to the butterfly valve. Secure the top cover back down.
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