TROUBLESHOOTING ONE-CYLINDER
ENGINES
Living on a farm, homestead, or just a small country estate,
we often find much of the repair work falls on us. Home
repairs, appliances, and oh Lord, that ever-present one-
cylinder engine.
One-cylinder engines are most common in sizes from 2 to 12
horsepower, carrying with it the same basic characteristics
of any gasoline engine. Trouble-shooting the one-cylinder,
however, is somewhat different from the 4, 6, or 8-cylinder.
When larger engines (those in autos with 4 or more
cylinders) are having problems, they will usually run. Not
always smooth, but they run. The one-cylinder, when
something is wrong, may not even start, let alone run. For
that reason the one-cylinder engine is a harder one to
trouble-shoot.
Trouble-shooting the small engine, if you know how, can save
you quite a bit of your hard earned cash. Usually when one
doesn't start we buy a tune-up kit when it needs nothing more
than a new plug. Worse yet, the plug may just need cleaning.
If we decide something is wrong withe the carburetor we
usually buy a new one. Needless to say, much of the work
and expense that goes into the repair of a small engine is
unnecessary. We work by trial-and-error until we've spent the
price of a new engine and then take it to a mechanic who
works on it for 20 minutes and charges us for a full
hour at $24 per hour or more - just for labor!
Another important thing to remember about a small engine if
you live close to a small town is it's sometimes a hard one to
get repaired. Even though there are more mechanics today
specializing in small engines, there are still towns that don't
have a single small engines mechanic. Auto mechanics
usually don't work on lawn mowers or power chain saws.
There are only two things that a small one-cylinder engine
must have to run. It must have an adequate supply of fuel,
and the fuel must be getting into the engine. Then there must
be an adequate supply of ignition spark. These two points
are known to mechanics as "gas and fire".
First, let's take a closer look at the gas. Before you go a
single step farther, find the air adjustment valve on the
carburetor. Turn the screw to the right as fall as it will go. Now
turn it back to the left 2-1/2 turns. If the carburetor works
function at all, it'll work right there.
To test to see if the carburetor is getting gas, remove the air
breather. Set your troddle of choke (or start) and pull the rope
starter. Look into the top of the carburetor. If gas is visible it
is unlikely that the problem is with the carburetor. If you think
the problem might still be gas, try this one. Using the palm of
your hand, cover the opening on top of the carburetor. Pull
the rope starter again. Pay close attention (by feel) which
way the air is going through the carburetor. Is it sucking your
palm into the carburetor or is it trying to blow it out? If it
blows, you have problems with your valves. Chances are one
of them is burned and will need replacing - a charge of $100
or more if you take it to the shop but less than $20 if you do it
yourself.
The next point to check if the engine still isn't running is the
fire. The fire consists of the coil (or magneto), the breaker
points and the plug. A coil will usually outlive the engine
twice-over. The points and plug, however, are a different
story. They usually need replacing at least one a year - call it
an annual tune-up.
To check the points in the engine, remove the plug wire. Hold
it with insulated pliers about 1/4 inch from the end of the plug.
Pull the rope starter. If the points are breaking properly, you
will be able to see the spark as it jumps from the wire to the
plug. If no fire is seen, replace your points.
When you check the wire, there might be a spark coming to
the plug. If it is getting to the plug, it is possible that it isn't
getting through it. Remove the plug from the engine. Put it
back on the plug wire and pull the rope starter. Be sure the
plug is grounded against the engine. If no fire is visible
coming from the end of the plug, replace the plug with a new
one.
The small engine is popular all over the world and will be with
us for many years to come. You would do well to learn to fix it.