How to Rebuild a Small Engine How to Rebuild a Small Engine

What You'll Need
Engine
Wrenches
Gaskets
Oil
Oil filter
Spark plugs
Carburetor kit
Air filter

A small engine is much like a larger engine in many respects. It has many of the same components and you need similar skills to disassemble and rebuild it. It’s not something to be attempted by a novice. At the very least, you should certainly have the service manual as a guide and videoing yourself as you disassemble can prove very helpful for retracing your steps.

Step 1 - Cylinders

You need to inspect the cylinders for wear and tear as well as the pistons. Where there is obvious signs of wear, the cylinders will need to be bored out. Also, check the crankshaft for any wear and recondition if necessary. Make sure all the components are completely clean since dirt in the cylinders will cause further wear and cause possible malfunction.

When all components are in a satisfactory condition, reassemble the cylinder. You will need to pay special attention to the crankshaft clearance. Follow the instructions in the service manual for your particular engine.

Step 2 - Gaskets

You should have discarded the old gaskets when you tore the engine down and you should have bought new gaskets to replace them. The main one will be the head gasket on the engine cover.

Place the gasket on the cover with the bolts going through the holes and place the cylinder head on top. Slowly use your wrench to tighten the bolts. Go around gradually but don’t tighten any individual bolt down firmly until all of the others are hand tight. Check there are no gaps between the head and the cylinder.

Step 3 - Carburetor

Before you fit the carburetor back on the engine, you should disassemble it and clean it, making sure you replace parts from a carburetor kit. Follow the instructions to take apart the carburetor and reassemble it once clean, paying strict attention to the screw settings as these regulate the fuel and air mixture to the engine. Too much of one and not enough of the other will cause misfires. When the carburetor has been clean and reassembled, put back on the engine and attach the fuel line.

Step 4 - Oil

Remember that there will be no oil in the engine at this point. Before adding any, you need to screw on a new oil filter. Screw on to hand tightness then use an oil filter wrench to tighten all the way. When you’ve done this, add the correct amount of oil, paying careful attention to be certain you’ve used the proper oil weight.

Step 5 - Spark Plugs

Don’t try and re-use your old spark plugs. Buy new ones and gap them correctly with a gapping tool. Screw the plugs in and attach all other wires including the spark plug wires with the other end running to the distributor. Attach the ignition wires to finish.

Step 6 - Fuel

Check the fuel filter and the fuel pump. Since you’ve cleaned the engine, the best thing to do is replace the fuel filter at this point. Now fill the fuel tank. Your small engine will be ready to start again. Remember to adjust the mixture as necessary.

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