Handy Tips When Rebuilding Your Small Engine

Handy Tips When Rebuilding Your Small Engine

Most importantly, you will need the service manual for the engine you are rebuilding. Consult the manual for specific recommendations and engine tuning, then follow the steps below as a guideline when rebuilding your engine.

Getting Started

To start, disconnect the spark plug and battery cables. Then drain the oil from the engine and remove it from the equipment. Dirt can be unforgiving, so ensure the engine is clean. Move the engine to a clean workplace and begin disassembling the engine with the help of your service manual. It may be handy to use a video camera to film yourself taking the engine apart, that way you can see where each part came from.

Taking The Engine Apart  

As you are taking the engine apart, look out for any wear and tear. Important things to look out for are signs of discoloration (caused by heat baking the oil into the part), aluminum that has melted and stuck to other components, scrapes and scarring. It is important to identify any issues so you are able to avoid another costly breakdown. If you do not fix the cause of the failure it will probably happen again. A general rule of thumb to follow would be, if the rebuild will cost you more than 50% of a new engine, you would be better off replacing the engine.

Inspecting Parts

Now that the engine has been taken apart, it's time to take some measurements. Consult your owner’s manual for specific measurements. Taking accurate measurements of the cylinder bore is critical to ordering the correct part. While the engine was operating the piston rocks from side to side as it travels up and down the bore. This causes the bore to become egg shaped. Also the bottom of the bore wears more than the top. New Rings will not seal in a out-of-round cylinder. Cylinders can be renewed by boring to Oversize. Oversize is usually .010", .020" or .030" larger than the standard bore which will be listed in your manual. You will want to use the smallest OS that will repair the cylinder so that the engine could be rebuilt more than once. The crankshaft may also need to be reconditioned. If you do not have the tools to take these measurements, just take the parts to the local machine shop and have them reconditioned. The machine shop will then tell you what "oversize" piston and ring set you will need. They will also tell you what Undersized connecting rod will be required if the crank was turned down to correct wear.

Ordering Parts

Time to order the parts you need. Some engines have rebuild kits available, whilst with others you will need to order parts individually. You will definitely need gaskets, and it would be wise to replace the oil filter, air filter and spark plug. While your at it, give your carburetor a rebuild with a kit. 


Add the proper oil and run the engine for 5 minutes or so at near full throttle. Allow the oil to cool and change it. This will remove the first break-in cycle metal deposits. Some engines require that the head bolts be re-torqued after the engine cools down completely. Check the manual for your manufacturers recommendations. After 10 hours or so, change the oil again. Keep checking the oil frequently as a new or rebuilt engine will use more oil during their breaking in period. 

Good Luck  

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