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CAUTION:  Exercise Extreme Caution when working around ignition systems as used on automobiles, trucks and motorcycles.  Severe electrical shocks can result by touching any of the ignition components, such as ignition coils, spark plug leads, spark plugs, especially when the engine is in operation.  Even battery and coil ignition systems can produce dangerous electrical currents, usually between 20,000 and 40,000 volts, during engine operation.  Electrical shocks can be very dangerous to persons using heart pace makers or other devices. 

Routine readers of this Service section of the Newsletter may recall the past articles on Batteries and Engines.  Both routine readers and those not so routine, may find it helpful to review same as a refresher.  Numerous web-sites are available for those who desire more in depth knowledge of ignition systems, or as an alternative, a good library and or bookstore will also be helpful and informative. 

Every Great Band Has Its Players …So Does The Battery and Coil System…Each Component Is a Player

The Battery…Where it all Starts
The battery as mentioned supplies electrical power to all the ignition components.  It must be up to the job in terms of electrical power, because a low battery will result in a weak spark.  Batteries should have a good charge -- around 12.5 volts.  Please take the time and read the prior IHM Newsletters on Batteries, as there will be many hints for the battery alive and well.

The Points…Its Like The Band Leader…He Sets the Tune
The points are very much like the light switch in your house.  You turn on the switch and the lights come on.  In the battery and coil ignition system, the points are used to make sure the spark plugs “spark” at the right time.  These points are mounted on the front timing case and are opened by the cam lobe (bump) which is part of the advance unit.  As indicated, the timing of when the points open is critical, thus the points are mounted on a points plate which can be rotated.  Rotating this plate will change the time at which the points will open, relative to the rest of the rotating engine parts.  There are timing marks on the flywheel so that correct timing (opening of the points) can be set.  This timing can be verified by aiming a timing light through the timing hole in the crankcase and onto the flywheel marks.  As the engine is accelerated, the weights of the advance unit spin outward and force the points to open sooner.  This is necessary to ensure the ignition timing remains “in-time” for higher engine speeds.  Ignition (spark plugs “sparking”) must take place sooner due the higher engine speed and the need for a controlled burn of fuel within the cylinder.  For correct timing at idle, the “S” mark (for “slow”) on the flywheel must be aligned to the slash mark in the timing hole.  For correct timing at higher speeds, the “F” mark (for “fast”) must be visible via the timing light flashes (each flash means the spark plugs have sparked) at 3,000 rpm.  Just envision the points as a simple on-off switch.  As mentioned, every time the points are opened the spark plugs spark because the magnetic field inside the coils collapses thus stepping up the volts from 12 to approximately 20,000 to 40,000 volts.

Hint:  Before installing a new set of points, clean off the area where the two ends of the points contact each other.  They are usually coated with a preservative to prevent corrosion.  Lubricate the advance unit where the rubbing block of the points rides, dry rubbing blocks will make a squealing noise.  Ensure proper routing of the points wire to the condenser and glue the foot of the rubber vent tube to the front timing cover.  If that is not done, you stand a chance of cutting the wire when installing the front cover.  When installing a new set of points always replace the condenser as well.  Tighten all screws which secure the points to the points plate.

The Condenser…It Prevents Sparks Where They Are Not wanted…Thus There Is No Bad Music
The condenser is used to ensure that no sparking occurs between the points contacts when the points open.  The back EMF current from the coil will try to jump the gap as the contact opens, and over time the points will transfer metal from one contact to the other.  In addition to reduced efficiency, this slowly closes the open points gap, which will change the ignition timing.  The condenser absorbs the electrical current as it tries to jump the gap.

Hint:  Condensers wear out, thus replacement should be performed when the points are replaced.  We old timers always carried a spare set of points and a condenser in the tank bag. 

                Condenser in Action                                No Condenser - Points Burn

The Ignition Coils…They Are Like the Brass of the Band… They Add the OOMPH to the Concert…They Make Sparks Happen
The coils are used to provide “spark” for the spark plugs and thus ignite the fuel/air charge within the cylinder.  As stated previously, the coils are energized when the ignition switch is turned ON.  12 volt current enters the primary windings and create a magnetic field around the coil’s iron core.  Once the points open, the primary field (magnetic) collapses and the 12 volt electrical current is stepped up to 20,000 to 40,000 volts in the secondary windings which goes the spark plugs and jumps the gap as a spark.

Hint:  Ignition coils get quite warm while in use, thus the coils are filled with oil to help keep them cool.  The color of the spark at the spark plug should be blue-white in color.  A red or yellow or very small spark indicates problems with the ignition coil side of the ignition system.  Check your electrical connections at the ignition coil itself.  The use of an ohmmeter will help determine if the windings of the primary side of the ignition coil may be open or have the incorrect resistance.  Check by touching the + and – sides of the coil with a the ohmmeter.  The secondary windings can be checked the same way.

Quick Check:  Caution -- turn off the fuel petcocks before performing this simple test to see if you have spark.  Remove the spark plug from each cylinder and lay the spark plug with the secondary wires attached onto the cylinder head.  Turn engine over via the starter and observe the color and size of the sparks produced by each spark plug left and right cylinders.  They should be large in size when jumping the gap at the spark plug and white/blue white in color.  You can also perform the above with the engine stopped and with access to the points via the front cover -- you can just manually open the points and observe the spark plugs as noted above for the proper spark.

The Secondary Wires…. the Path for the Sparks
The secondary wires which are connected to the tower of the ignition coil end and to the metal or plastic caps which connect to the spark plug.  These wires carry the 20,000 to 40,000 volts produced by the ignition coil to the spark plugs.  Caution!  Do not remove or touch these wires and or any of the ignition system components, especially those used on modern vehicles, while the engine is in operation. Risk of Severe shock and or burns can result.  Over time the wires become hard and will internally break, thus the electrical current will not be carried with its full potential to the spark plugs, resulting in a weak spark.  The resistance of these wires should also be checked when a weak spark is detected.  Spend some time and look inside the metal or plastic spark plug cap, any sign of black streaks, corrosion, cracks, etc., which indicate the need for replacement.  Like anything electrical, always check the repair manual for the correct values and settings.

The Spark Plugs….they are like the Solo Artists When making Music…They Are Creating “Sparks”
The spark plugs are the final part of the ignition system, and via a gap between the electrodes the high voltage electrical current (20,000 – 40,000 volts) must now jump across and ignite the fuel/air mixture.  From that point on combustion occurs across the combustion chamber and the piston is pushed downward on its power stroke.

Hint:  Spark plugs come in different sizes and heat ranges, thus it is very important to install and use only the correct spark plugs for your model of motorcycle.  Look in the owner’s manual to ensure the correct spark plug is being used.  Prior to installing the spark plug check the electrode gap using a spark plug gap tool, or, in a pinch, a feeler gauge.  Again, see the manual for specifications.  Never install a spark plug that has been dropped, as the ceramic may have internally cracked and there is risk of it becoming loose and causing internal engine damage.

Replacing spark plugs at recommended intervals will produce benefits in terms of power and fuel economy.  The ceramic which surrounds the center electrode of the spark plugs actually glows during the operation of the engine.  This is why the heat range of the spark plug is critical and any deviation from the proper heat range will cause poor running (heat range too cold) or severe engine damage (heat range too hot).  Apply a small amount of anti-seize compound to the threads of the spark plug, but ensure it does not come in contact with the electrodes.  Carefully thread the spark plug into the spark plug of the cylinder head and use a torque wrench to tighten to the correct value.