Leaf blowers commonly use a two-stroke internal combustion engine. These engines have very specific fuel requirements for their operation. They require two-stroke engine oil added to the gasoline before it enters the leaf blower's fuel tank. If unmixed gas is ever used in the leaf blower, piston and cylinder damage can happen within seconds.
Two-stroke engines such as a leaf blower's don't use an oil pump to lubricate the crankcase and piston. The lubrication comes straight from the fuel and protects the piston and crankcase by developing a thin layer of protection on the walls. This fuel mix requires an air-cooled, two-stroke oil mix designed for inboard engines. Most manufacturer's set their own mixing specifications, which generally range from 25-to-1 up to 50-to-1. However, all of these engines require a mixed gas to prevent serious engine failure.
Unmixed regular unleaded gasoline will burn inside the cylinder. However, the temperature at which it will burn will be too great for the piston and cylinder to handle, which will result in a seized piston stuck inside the cylinder. This overheating of the piston rings and seals can happen in less than one minute, which is why you should never put unmixed gasoline into the fuel tank. These repairs can be fixed only through time-consuming, expensive repairs, often more than the cost of a new blower.
What to Do?
If you used unmixed unleaded fuel in the tank and ran the engine until it shut off on its own, you are out of luck. Nothing can reverse the internal damage done to the piston and crankcase. The only way to fix these is to split the crankcase, take out the piston and replace it with a new one as well as get new seals and gaskets. The price for these repairs may exceed a new blower, so always ensure the fuel is mixed properly before using it. Never let anyone who isn't aware of the manufacturer's fuel specifications put fuel in the leaf blower.
If you filled the tank with unmixed fuel and haven't ran the engine into overheating, you may be in luck and just may save your engine. Dump out any fuel left in the tank. Remove the fuel tank, gas lines and carburettor from the engine. Disassemble the carburettor, and clean it thoroughly with a brush and rag. Wash the fuel tank out with soapy water, and let it dry thoroughly before reinstalling it. Replace both gas lines, and mix a fresh batch of two-stroke engine fuel. Always shake the gas mix before each use.