Let's look at doing a complete engine rebuild to an engine that has not been properly maintained. These are the steps I follow when I do a rebuild. You see, I believe their is more to a rebuild then rings and a new spark plug. An engine rebuild is a major project and proper preparation is needed. Start by purchasing a repair manual for the engine you are working with. This manual is invaluable in giving specifications and repair procedures.

Ideally, the preparation for a rebuild starts by a visual inspection, followed by running the engine if possible and observing the problems it has.

• Check the oil to see if it is low or dirty.
• Check the fuel for contaminates and freshness.
• Examine the spark plug to see if it has oily carbon on it.
• Notice any fuel or oil leaks, blown gaskets, hoses etc.
• Look for loose linkages, plugged cooling fins, a loose governor shaft or carburetor shaft.
• If the engine is severely damaged and won't run, look for cracks or holes in the block.
• Take a good look at the air intake system. Has dirt been entering the carburetor air intake?

Start the engine and observe any blue smoke, engine noises and lack of power. Does the engine misfire or rattle badly? Does the governor work ok? Does the engine idle ok? Is excessive smoke (blow-by) coming from the crankcase breather tube? All of the above can give you a good indication of what you will find when you disassemble this engine. If the engine does not smoke badly or make unusual noise, but lacks power, it may only need a valve grind or tune-up. Carbon buildup can be a real problem on gensets, pumps etc.

At this point you have decided the engine is smoking and needs a rebuild. I like to start by removing all the shrouding and use either compressed air or a pressure washer to clean the engine thoroughly before opening it up. You may want to take it to a car wash. This gives you a clean unit to work on. Leave the air filter on for this and duct tape the exhaust outlet and fuel cap vent. If you pressure wash the unit, blow dry with compressed air.

Most repair manuals give a disassembly procedures which you may follow if you like or use a variation of the one below. If you own a digital camera, take pictures of the governor springs, linkages and other items you may want to look at when it comes time to reassemble. Here's a suggested order of disassembly for an L-head engine:

• Remove the fuel tank, carburetor and governor linkages.
• Remove the valve cover and breather assembly.
• Remove the cylinder head and valves and inspect.
• Next take a good look at the valve seats and valve guides.
• Look for a wear ridge or carbon near the top of the cylinder. You will need to remove this before removing the piston.
• Remove the flywheel next, then open the crankcase up and remove the rod cap. You may want to use Plastigage and check the rod clearance at this time.
• Remove the piston next. I like to remove the top ring and fit it back in the cylinder to check the ring gap.
• The camshaft and crankshaft can come out next. You now should pretty much have a bare block setting in front of you.

Now comes the really important part and you get to use your new repair manual. In the manual you will find specs and measurements on everything in the engine. Spend plenty of time measuring and listing all the parts that do not meet minimum or maximum specs. Note any excessive wear or scratches from dirt entering the engine. You don't want to cut corners here, because it's the difference between a good rebuild and a comeback (dirty word). It does no good to put a set of new rings in a cylinder that is worn beyond specs. If you don't have the equipment to measure properly, take it to a local machine shop and pay them to "mic it up" for you.

Rebuild Kits: Most engine companies do not sell rebuild kits and the ones being offered on the market are often from aftermarket companies or overseas sources. I recommend using genuine OEM replacement parts on your rebuild. Start with a gasket/seal set and add to this the parts you need after you get done with the measuring procedures above. These may include such items as a piston assembly, rod assembly, valves, governor and carburetor kit. This way you will get just the parts you need in the correct sizes, assuring a quality job. Don't be mislead by aftermarket rebuild kits being a cheap shortcut to success, it's the care given to detail, plus the correct quality parts that make the job last.

We will not go into reassembly here as this can vary between models. Pay close attention to recommended procedures and torques. Make sure you understand how the governor linkages connect and any static governor adjustments that need to be made. You usually reassemble by building up a short block, then adding the components as groups in the reverse order that I disassembled them. With the spark plug out, turn the engine over often to feel for any binding or rubs. Apply plenty of oil on the internal parts of the engine when installing them. Don't forget to include new air, oil and fuel filters as part of your rebuild. Last but not least, keep it clean!!! Remember, contamination is your enemy. I hope this information gets you going in the right direction on your engine rebuild.

Also see Step by Step Two Stoke Carburetor Rebuild

Also see Carburetor Rebuild, Loose Valve Seats,  Carburetor Troubleshooting Chart or My Engine Won't Start for more troubleshooting.

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