Just 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.
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.
Materials:
Motorcycle service manual
Replacement air filter
Replacement spark plugs
Socket wrench
Torque wrench
Spark-plug gapping tool
Screwdriver
Antiseize lubricant
Dielectric grease - After unplugging the spark-plug wires, unscrew the spark plugs (figure A) and remove them.
- Using a gapping tool, gap the new spark plugs (figure B) to the specifications recommended in your service manual.
- Apply some antiseize lubricant to the threads on the new plugs.
- Install the new plugs and, using a torque wrench, tighten them to the torque specifications recommended in your service manual.
- Apply a small amount of dielectric grease to the contacts on the plug-wire connectors (figure C), and reinstall the plug wires.
- 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.
- Install the new air filter according to the manufacturer's instructions (figure E).
- Replace the air-filter cover and tighten it down securely.
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 fuel filter.
Materials:
Replacement parts: plugs, plug wires, points, condenser, fuel filter, etc.
Motorcycle service manual
Socket wrench
Torque wrench
Spark-plug gapping tool
Screwdrivers
Needle-nose pliers
High-temperature engine lubricant
Antiseize lubricant
Dielectric grease
- Unplug and remove the old spark-plug wires (figure F).
- After unplugging the spark-plug wires, unscrew the spark plugs and remove them.
- 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.
- 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).
- 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.
- 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.
- 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.
- 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).
- 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 service manual.
- Apply some antiseize lubricant to the threads on the new plugs.
- Install the new plugs and, using a torque wrench, tighten them to the torque specifications recommended in your service manual.
- Apply a small amount of dielectric grease to the connectors on the new plug wires, and reinstall the plug wires.
- 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).
- 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 old filter, replace it with a new one and reinstall the clamps.
RESOURCES :
The Complete Idiot's Guide to Motorcycles
ISBN: 0028624165
Author: editors of Motorcyclist magazine
Some motorcycles provided by Knoxville Harley Davidson
Knoxville Harley Davidson
5800 Clinton Highway
Knoxville, TN 37912
Phone: 865-689-2454
Toll-free: 800-637-6386
Web site: www.smokymtnmall.com/mall/harley
Motorcycle Tuning: Two Stroke
Model: 075061806X
Author: John Robinson
(1994)
To order this title from Amazon.com, click here.
Butterworth-Heinemann
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