How to Light Your Fire... Ignitions
By Scott Holton, J&P Tech Hello!
It’s time for another edition of Tech Talk. This month’s edition will discuss
Ignitions. It is our objective today to give a little history of what has been
used in the past and give you some ideas of things to use to improve
performance.
Mother Harley® has used a variety of ignitions over the years. In the early days
(prior to 1979) a Points & Condenser system with some type of advance was
used. Prior to 1965, advancing and retarding the ignition was a manual thing
controlled by the left handgrip. Many unsuspecting souls where pitched over
their handlebars attempting to kick over a bike that had not had the ignition
retarded.
In 1965 with the advent of electric start, automatic advance was developed.
While the auto advance is very dependable, but is also high maintenance. With
the points the rubbing block can wear away, material can transfer from one
contact to the other, and the advance mechanism can wear out. These things will
all hurt performance if not attended to.
In late 1979 Harley® stepped into the electronic age with an ignition from
Magnavox that eliminated the points and condenser, but retained the mechanical
advance. This was a step in the right direction, but there were still some
reliability issues with this system. It was not unusual for riders to have this
system removed and the earlier points ignition system installed. The problems
encountered here gave Harleys® electronic ignition a bad name. It would take
years for them to overcome this.
In 1982 The V-fire III ignition made its debut. This system is completely
contained in a black box more commonly known as a module. We actually get rid
of the advance unit because the module has a couple of advance curves built in.
Triggered by a rotor cup and a hall effect transducer this system requires no
maintenance. Due to the different ignition requirements presented by a light
(Sporty) or a heavy (Dresser) motorcycle a Vacuum Operated Electric Switch
(VOES) that can be set at different vacuum level handles changing the advance
curves. Under heavy load conditions the ignition is retarded. This ignition
soon proved to be very reliable but not the absolute best for performance.
All Harley® ignitions that came direct from the factory prior to 1999 fire both
spark plugs at the same time. One twin tower coil is triggered. One plug fires
producing power, and the other plug fires during valve overlap. The “street”
name for this type system is dual fire.
Finally some enterprising folks said, “let’s get rid of that wasted spark” and
products were developed to do just that. (These Dual points systems were the
predecessor of today’s Single fire system). The Dual points single fire system
was installed in the early sixties by the Harley® dealer network. The factory
developed the parts, but would not install them, the dealer had to. The later
developed Single fire is where each cylinder fires independently of the other.
The street name for this type ignition is single fire.
Crane, Dyna, & Spyke are companies that offer both single fire and dual fire
ignitions. H-D® itself has gone to the single fire type ignition on today’s
TC88. Each brand of ignition has its advantages and disadvantages. A Duel fire
system is the same type that has been around forever and if you select one of
this type, the coil that your bike currently has will usually do the job. But a
single fire ignition has the advantage of better starting and reduced low speed
vibration. These advantages are distinct and very noticeable. Its drawbacks are
the increased initial cost and the requirement that a different type coil be
purchased.
Crane, Spyke and the Dyna 2000 are true electronic ignitions that are a distinct
improvement over the stock H-D® module. The Dyna-S is very reliable and an
improvement over stock but requires an advance weight set-up. Maintenance of
the advance then rears its ugly head. Crane and Spyke do not require an advance
weight set up. Once they are set-up and timed correctly they are truly set and
forget type systems.
For those of you with a generator bottom end that desire the improvement given
by lighting the fire more efficiently, J&P® offers replacements for your
points circuit breaker from Mallory and Spyke to take advantage of modern day
technology.
Remember that to make power there are specific things we must do.
-
We can get more air (thus more fuel) in and out increasing volumetric
efficiency. This is accomplished with carb and pipe changes.
-
We can increase the quality of our ignition. This increases combustion
efficiency. Note: Remember that by getting a more thorough burn, it’s not
unusual to have to increase jet size (more fuel, more power) to take advantage
of the improvement.
Generally the other 2 ways to make power (Mechanical and Thermal efficiency) are
not practical for the street. If we get enough interest, maybe these are
subjects for a future edition of Tech Talk. T
As always, feel free to give us a call if you have any questions.
