Troubleshooting One-Cylinder Engines

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 ar 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.