There seems to be an increasing number of two-cycle engines with a scored piston and cylinder, yet these units do not have any of the usual abnormalities that can cause scoring. For example, a new line trimmer that is assembled and tested before it’s sold to the customer is in excellent operating condition. A few days later the customer is back with the unit describing that it ran for a short time after he refueled, but that it suddenly stopped and he couldn’t pull the starting rope!

When the mechanic removes the muffler to check the condition of the piston and cylinder, he finds that they have been badly scored in a way that suggests a lack of oil in the gas/oil fuel mix. Further investigation shows plenty of oil in the fuel mix. The carburetor hasn’t been tampered with and there are no air leaks in the engine (air leaks can be tested for by pressurizing the crankcase with special equipment).

This engine should not have seized! However… it’s very well frozen.

This scenario has become so common that most two-cycle engine manufacturers make the topic a regular part of their annual dealer update schools.

What is the cause of this mystery? There is good evidence that most of these engines are suffering from alcohol damage. The first thing the customer says is that he purchased fresh gas and nowhere on the pump was there a sign labeling it gasahol or warning of any alcohol content in the fuel. However, when testing the fuel in his engine a substantial amount of alcohol is found.

The next questions are why is the alcohol present and how did it get there?

Alcohol as a motor fuel does have some advantages. It’s made from farm waste products and is therefore renewable. It’s an inexpensive way to raise octane ratings and it burns clean, thus improving the environment. There are also government incentives to oil companies to add alcohol to gas and according to regulations if the amount is less than 10% the consumer need not be informed of its presence in the gas they buy.

With all of these advantages, alcohol will not work well as a two-cycle engine fuel. The primary problem is that alcohol is very corrosive and will attack many of the materials that compose your engine. A second problem is that alcohol and two-cycle oils will not mix. Many of the popular two-cycle oil mixes have been tested in alcohol and the oil acts as if it’s in water, forming into little balls and sinking to the bottom instead of floating on top as it does in water. One synthetic oil has been found to mix in methanol, but not alcohol. How its reacts in gas has not yet been determined.

While the objective of this article is to inform you of an existing problem and not endorse any products, there are ways to limit your risk. First, you might have to pay a little more for gas. It seems that those customers that have been having problems have been purchasing gas from discount stations. So, pay a little more and stick with the major brands. Also, use a fuel with an octane rating of at least 90ROZ (this will be listed on the pump). It has been shown that following this program will greatly reduce the incidence of piston damage.

And finally, have your dealer adjust the carburetor to the manufacturer’s recommended maximum RPM. Avoid making any adjustments yourself. Many people adjust the carburetor by sound rather than using proper instruments and specifications. This will only multiply alcohol related problems and cause further damage.

Enjoy the season and GOOD CUTTING!