Small engines are commonly used on lawn power tools such as lawn tractors, chain saws and snow blowers. Several things can cause an erratic performance in an engine's RPMs. To troubleshoot the problem, first check the RPMs in the idle speed and high idle speed positions. The procedure takes about 10 minutes.
Place the engine on a flat workbench.
Remove the spark plug wire from the spark plug located at the front of the engine. Remove the spark plug with the spark plug wrench, then inspect the spark plug. If the plug is dirty or fouled, replace it. Plug the spark plug wire back on to the spark plug.
Turn on the tachometer. Wrap the lead from the tachometer around the spark plug wire.
Start the engine, then move the throttle to the SLOW position. Take the reading from the tachometer. Refer to the specification page in the operator's manual for the correct operating range.
Move the throttle to the FAST position, then take the reading from the tachometer. Refer to the specification page in the operator's manual for the correct operating range.
Locate your mower' s spark plug. With a socket wrench, remove the old spark plug.
Refer to your mower' s owner manual to check the required gap measurement for your spark plug. Once you have determined the required gap, all you need to do is measure the gap on your new spark plug. Make adjustments in the gap to match the manufacturers specifications for your specific mower.
Once you have altered or creating the proper gap in the spark plug, simply screw in the new plug. Be careful not to screw in the spark plug too tight.
Disconnect the coil wire from the spark plug by gently pulling on the wire "boot" connecting the coil wire to the spark plug.
Using a spark plug wrench, remove the spark plug from the engine by turning it counter-clockwise. It will take several revolutions of the plug before it can be removed.
Reconnect the boot to the plug by pressing it firmly back on top of the Spark Plug. You should be able to feel the connector inside the boot "snap" back on the plug.
Rest the end of the plug (opposite the boot) against the engine. Turn the engine over and visibly check the plug where it touches the engine. If the engine is working correctly, you should see sparks at the end of the plug. If not, replace the plug with a new one and try again. If there is still no spark, the engine magneto may need to be replaced.
If the plug shows spark, remove the boot from the plug, and screw the plug back into the engine. Tighten the plug to the manufacturer's rated torque.
Reconnect the boot to the plug by pressing it firmly back on top of the Spark Plug until you feel the connector inside the boot "snap" back on the plug.
Place the chainsaw on a flat work bench.
Check to see if the spark plug wire is exposed. The spark plug wire is black and is connected to the spark plug. If its not exposed, remove the air filter cover located directly above the carburetor. This will expose the spark plug wire.
Turn the tachometer into the on position. Wrap the external lead from the tachometer around the spark plug wire.
Start the engine and let it idle. Check the reading in the idle position. Most chainsaw operate between 2500 to 3000 RPM's. Check your model's service manual for the proper range.
Advance the throttle to the full throttle position. Check the reading. Normal RPM's in the full throttle position are between 11000 to 15000. Check your model's service manual for the correct operating range.
Use a hose and nozzle to wash grass from the underside of the mower and spray clean the top when the engine cools.
Unplug the spark plug wire then check the lawnmower blade for chips and nicks. Ideally, the blade should be sharpened during the mowing season to maintain a good cut or replacement if dull and damaged.
Check the oil dipstick for proper level then fill accordingly by locating the dipstick under the cap with the word "oil" or oil can picture and read the level marker at the bottom of the stick.
Change the oil each year; see your manual for the process that usually requires a wrench and oil-draining pan.
Replace the spark plug each year or two. Use a special spark plug socket that's deeper and unscrew the plug noting the printed number on the plug for the exact type needed.
Get a new air-filter each year. Locate in the small housing box that snaps open and pull the old filter out. Take the small filter to a home and garden shop or check the product number in the manual.
Store the lawnmower at the end of the season to maintain consistent service. Read the manual, and always drain the gas and then start the mower to burn the remaining fuel from the lines.
Place the drip pan beneath your snow blower's oil drain plug. The drain plug is on the righthand side bottom of the engine block. Remove the plug by hand by twisting it off to the left, or use a pair of pliers to loosen it if it is too tight. Allow all the old oil to drain out of the engine, then replace the drain plug.
Open the oil fill cap at the middle top of the engine and add 26 ounces of SAE 5W-30 oil.
Remove the spark plug wire. Fit the spark plug wrench over the spark plug and turn it to the left to remove it.
Set your spark plug gap tool to .030 inches and use it to set the gap on your new spark plug.
Screw the new plug in by twisting it to the right until it is tight, then replace your spark plug wire.