Quck answer
If your lawnmower has low compression, there are several steps you can take to fix it:
1. Check the spark plug: A worn-out or dirty spark plug can cause low compression. Replace it if necessary.
2. Inspect the valves: Check if the valves are properly adjusted and seating correctly. Adjust or replace them as needed.
3. Check the piston rings: Worn or damaged piston rings can reduce compression. Replace them if necessary.
4. Clean or replace the carburetor: A clogged carburetor can affect compression. Clean it thoroughly or replace it if needed.
5. Check the head gasket: A faulty head gasket can cause low compression. Inspect and replace it if necessary.
By following these steps, you can fix a lawnmower with low compression and ensure it runs smoothly again.
Gas-powered lawnmowers are equipped with combustion engines that are similar to the ones found in motor vehicles. The term “compression” refers to the pressure that builds up inside the piston chamber when a combination of fuel and air is compressed and ignited by a spark. This explosion pushes the piston outward and causes the crankshaft to rotate. A decrease in compression can occur due to worn pistons, worn piston seals, or bent or broken push rods.
Step 1
Locate the ignition wire that connects the spark plug to the distributor. Remove the wire from the spark plug by firmly grasping the base and pulling it off. Try turning the spark plug by hand. If it is loose, compression may be escaping through the gap. Use a ratchet set to tighten the spark plug securely, and then try starting the engine again.
Step 2
Inspect the bolts that secure the top of the cylinder head in place. These bolts are typically positioned around the outer edge of the head. Loose bolts can cause compression to leak from the cylinder. Use a ratchet set to tighten any loose bolts, and start the engine again.
Step 3
Remove the cylinder head cover and check the push rods and valve lifters for any signs of damage or bending. Damaged or bent parts can prevent a tight seal in the cylinder, resulting in decreased compression. If any parts are broken or damaged, they need to be replaced.
Step 4
Determine whether worn valves or worn piston rings are causing the low compression. Remove the spark plug and pour a small amount of W30 motor oil into the open cylinder. Place a compression tester over the spark plug hole. Disconnect the ignition coil and locate the crankshaft at the front of the engine.
Step 5
Use a wrench to grip and rotate the crankshaft while the tester is in place. Read the gauge on the tester and compare the results to the recommended compression range provided by the lawnmower manufacturer. If the oil resolves the compression issue, the problem lies with the piston rings. If not, the issue may be due to worn valves.
