How to Rebuild a Lawnmower Engine
Trying to rebuild a lawnmower engine without the original owner's manual can be difficult, however, there are things that can be done to help the process.
Following the steps below can help a person know which steps he needs to follow to make sure that he does all of the general things he can to rebuild a lawnmower. More specific things might need to be done if individual lawnmowers require it.
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Things You'll Need
- Socket wrench
- Screwdriver
- Cylinder rings
- Piston rings
- Oil seals
- Oil
- Gaskets
Instructions
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1
Disassemble the engine. Disassembly for most lawnmowers is typically a pretty simple process. Starting with the engine cover, use a socket wrench or a screwdriver to remove all of the parts of the engine. As each part is removed, it should be cleaned with warm, soapy water. Also check to make sure that each piece is not too worn or too damaged to be reused. If a piece is, it will need to be replaced.
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After each of the pieces have been examined and it is ensured that only quality pieces are being used for the rebuilding, start to rebuild the lawnmower engine by torquing the head bolts. After this, do the same with the lawnmower rods. Lap the valves on the mower as well. Set the clearances by filing the valve stems. The clearance also can be set by grinding the valve stems.
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3
Measure the sizes of the cylinders. If one side of the cylinder is larger than standard-sized rings, the rings will not be able to seal the cylinder. A cylinder can be made to be oversized by boring it about .010 larger than the standard cylinder. Rings can be purchased that will fit oversized cylinders.
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Replace the gasket. Make sure that when a new gasket is put into place that it completely seals the engine. A gasket that leaks or leaves the engine exposed could lead a person to need to rebuild a lawnmower engine again in the near future.
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Replace the air filters, the oil filters and the spark plugs. When changing the spark plugs, ensure that the new plugs are tightly pushed into their places. A loose spark plug can make a lawnmower engine not work, even if the rebuilding was done correctly.
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Check the work that was done. The best way for a person to tell if he has done a quality rebuilding of a lawnmower engine is to run it on full throttle for three or four minutes and then allow the engine to cool down a bit before changing the oil. By changing this oil, a person is able to remove any of the metal deposits that may have entered the oil during its first cycle.
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Tips & Warnings
After 10 hours of operating, change the oil again. This will remove most of the remainder of metal deposits that may have found their way into the oil. Avoid using used air filters and used oil filters when a lawnmower engine rebuilding is done. These items are inexpensive and should be fresh.
Fumes from the gasoline in a lawnmower can be dangerous. Remember to drain the gasoline before working and be sure to work only in open and well-ventilated areas.
