Tuning your engine will keep your motorcycle in optimal running condition and will result in a safer and more enjoyable ride
ust as with automobiles, motorcycles need to be tuned up periodically to keep them operating at peak efficiency. In this demonstration we perform a tune-up on a newer model motorcycle as well as a 1972 Harley Davidson Superglide. There are some significant differences since the older bike uses breaker-point ignition while the newer one has electronic ignition.Tuning your engine will keep your motorcycle in optimal running condition and will result in a safer and more enjoyable ride.
Important: Following are the steps used to perform tune-ups on the two motorcycles used in our demonstration. This summary should be regarded as a general guideline only. There are likely to be differences in procedures for other motorcycle brands and models. Consult your motorcycle's service manual for specific information that you may need when tuning up your particular model.
Performing a Tune-Up on a Newer Motorcycle
For our new model tune-up, we replaced only the spark plugs and air
filter on a 1996 Harley Davidson 883 Sportster.
Motorcycle service manual
Replacement air filter
Spark-plug gapping tool
1. After unplugging the spark-plug wires, unscrew the spark
plugs (figure A) and remove them.
2. Using a gapping tool, gap the new spark plugs
(figure B) to the specifications recommended in your
3. Apply some antiseize lubricant to the threads on
the new plugs.
4. Install the new plugs and, using a torque wrench,
tighten them to the torque specifications
recommended in your service manual.
5. Apply a small amount of dielectric grease to the
contacts on the plug-wire connectors (figure C), and
reinstall the plug wires.
6. Once you've finished replacing the plugs,
proceed to changing the air filter.
Remove the air-filter cover (figure D) and remove
the old filter.
7. Install the new air filter according to the
manufacturer's instructions (figure E).
8. Replace the air-filter cover and tighten it down
Older motorcycles use breaker-point ignition system. With wear and use, the surfaces on the points contacts wear out and become pitted (as in the point assembly in the foreground). A good tune-up should include replacing the points and condenser as well as the spark plugs and air filter.
Performing a Tune-Up on an Older Motorcycle
In our tune-up demonstration on an older motorcycle,
which uses a breaker-point ignition system, we replaced
plugs, plug wires, points, condenser, air cleaner and in-line
Replacement parts: plugs, plug wires, points, condenser,
fuel filter, etc.
Motorcycle service manual
Spark-plug gapping tool
High-temperature engine lubricant
1. Unplug and remove the old spark-plug wires
2. After unplugging the spark-plug wires, unscrew the
spark plugs and remove them.
3. Inspect the old plugs for signs of wear, and compare
their appearance to that of new plugs (figure G). The
condition of the spark-plug electrodes speaks volumes
about the condition of the engine and how well it's
operating. Your service manual may feature a chart
showing varying conditions of spark plugs and the
corresponding causes for each. Sooty,black plugs, for
example, may indicate an overly rich fuel/air ratio, a
malfunctioning choke or a dirty air filter. Oily deposits
may be a sign of worn pistons or valves.
4. Before replacing the plugs and plug wires, proceed to
replacing the points and condenser. With a high-
compression engine such as the one on the cycle used in
our demonstration, it will be easier to turn the cam and
replace the points with the spark plugs removed from the
engine.Use a screwdriver to remove the screws holding
the points cover in place, and carefully remove the cover
and internal gasket to expose the breaker.The condenser
is located in this area as well (figure H).
5. Use the kick-start to turn the cam, advancing the cam
nut until the points are in the open position (i.e., with the
points separated by a small gap as in figure I). Positioning
the mechanism in this way before removing the old
points will make it easier to install the new points.
6. Using needle-nose pliers, carefully unplug the condenser
wire and remove the condenser. Use a screwdriver to
remove the screws that hold the breaker-points in place,
and to release the bracket holding the condenser in place.
Remove the points and condenser.
7. With the points and condenser removed, take advantage
of the opportunity to check the condition of the advance
mechanism on the cam while the area is clear of other parts
(figure J). The cam should be movable but should snap back
into place when released with a distinct return spring-action.
You may want to apply a small amount of high-temperature
grease to the cam in order to provide lubrication.
8. Install the new set of points and condenser in the same
manner as the old ones. Reconnect the condenser wire. Once
the points are installed, follow any manufacturer's instructions
and specifications provided in your service manual to set the
gap on the points (figure K).
9. After you've installed the plugs and condenser, go ahead
and install the new spark plugs. Using a gapping tool, gap the
new spark plugs to the specifications recommended in your
10. Apply some antiseize lubricant to the threads on the new
11. Install the new plugs and, using a torque wrench, tighten
them to the torque specifications recommended in your
12. Apply a small amount of dielectric grease to the
connectors on the new plug wires, and reinstall the plug
13. In our demonstration we upgraded the air cleaner to
a newer version with a larger housing. To do so, we removed
the old air-filter cover (figure L), the air-cleaner assembly
and the plate at the base of the air cleaner (figure M). We
then replaced the entire assembly with a new one (figure N).
14. As a final step, you may want to replace the inline fuel-
filter (figure O). To replace the filter, simply loosen the worm-
style clamps that hold it in place in the fuel line, remove the o
ld filter, replace it with a new one and reinstall the clamps.