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Lawnmowers - Care and Feeding


90% of running problems are caused by bad gas. Remember there is no chemical formula for gasoline. It can be anything that comes out of the refinery that remotely resembles gas. With increasing cost and scarcity, it is not getting any better. Gasoline will not store more than a month at best, unless fuel stabilizer has been added. Use only the best gas you can get. That means 91 octane or better. Do not use 87 octane. The cost difference is not significant when you are buying only one gallon. That amount is going to last as long as you should keep the fuel in storage. Of course, you should never leave fuel in the mower over the winter. Drain the fuel and then run it till it quits at season's end.

Consider the possiblity of installing a fuel shut-off valve between the carburetor and the fuel tank. This way you can turn off the gas, and run the machine dry of fuel, leaving the carburetor clean. The volatile gasoline evaporates, leaving a varnish film that plugs the metering jets in your carb. That is also why the machine may start on prime, but then die out. The gas tank may smell like old furniture varnish. Very bad!


You will save yourself a lot of problems also by using 30 weight oil, not the usual automobile multigrade oils. The multigrades contain a polymer molecule that is supposed to hook together to make the oil thicker when hot, and release and make the oil lighter when cold. This only works in the temperature range of a water cooled engine. In an air-cooled engine, the much higher temperatures will result in the oil "locking up" and becoming gummy until you can't pull the rope if the oil has been in there too long. It is always a good idea to be sure to change your mower's oil at the very least, once a year, and avoid multigrade oil.


Blade sharpness will affect the appearance of your grass. A dull blade will shred and shatter the grass blades (leaves), wounding the plant, and making your yard turn prematurely brown. If you want a nice green lawn, keep the blade sharp by sharpening at least every two months, or more often if you hit rocks or dog bones. Be sure the blade is checked and balanced at sharpening. A sharp blade is also easier on your engine, since it can run cooler and with less strain. A dull blade requires more power. This is especially true with mulching mower blades. Inspect the cut ends of your grass to determine if your mower needs sharpening. Shattered and frayed ends mean a dull cutting blade. Spark plugs seldom fail, but are changed just to make it look like something was done, or on just "general principles". Most plugs fail because of build up of carbon (oil) deposits. The center electrode insulator will be coated with a heavy black coating, and the space between the threaded shell and the insulator will be filled with black gunk. This causes the plug to short out and therefore not fire. A plug is worn out when the end of the center electrode has eroded rounded off and is no longer sguare and sharp edged.

Carburetor cleaning.

Before blaming the carburetor, do a normal cold start procedure for your machine. Only pull the rope about six times. If no start, remove the sparkplug and inspect it. Is the end wet? if dry, there is no fuel getting to the engine, and it therefore can not start. If it is thoroughly soaked, it is flooded from too much choke, or prime. Blow off and dry the plug and try again, no choke. If you have the dry plug condition, try putting about a quarter teaspoon of gas directly into the sparkplug hole and replace the plug. Now start, and it should run a couple seconds, then, if not getting fuel, it will die. Repeat a time or two and mabe it will clean out the carburetor. If not, you will have to service the carburetor.

Mowers with a float bowl carburetor are much easier to service. Most float bowl carburetor cleaning can be done simply by pulling the nut at the float bowl bottom, which turns out to actually be the entire metering jet assembly. You then can rod out the very tiny holes to clean the carburetor. Be very careful not to enlarge the holes! Use a smooth rod or wire, the correct size to fit the hole. Never a torch cleaner which is a little file actually. Simply re-install and you are ready to go. No re-adjustment necessary, unless someone fooled with the adjustment. Further cleaning requires more disassembly, but cleaning just the jets will get it most of the time on these float bowl carburetors. If the carburetor is mo