How to Light Your Fire… Ignitions

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June 29, 2010 | By: Scott Holton

Easily among the most forgotten performance enhancement today is your motorcycle’s ignition system. Adding additional performance parts can sometimes be a waste of time and effort if your motorcycle’s ignition system isn’t upgraded.   Today, we’re going to start off with a brief history of Harley-Davidson’s ignition systems, and then we’ll talk about some alternatives.

Mother Harley has utilized a variety of ignitions over the years. In the early days (prior to 1979) a points and condenser system with some type of advance was used. Before 1965, advancing and retarding the ignition was a manual thing, controlled by the left handgrip. Many an unsuspecting soul was pitched over the handlebars attempting to kick over a bike that had not had the ignition retarded.

With the advent of electric start in 1965, automatic advance was developed. While the auto advance was dependable, it was also high maintenance. The points rubbing block would wear away, material would transfer from one contact to the other, and the advance mechanism frequently wore out. These things all hurt performance if they weren’t maintained.

By late 1979, Harley stepped into the electronic age with an ignition 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 Harley’s electronic ignition a bad name and 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. Triggered by a rotor cup and a Hall Effect Sensor, 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 when it came to performance.

All Harley ignitions that came direct from the factory prior to 1999, with the exception of the ’98 and ’99 1200S Sportsters, fired both spark plugs at the same time. One twin tower coil is triggered and this fires both plugs at the same time.  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 they developed products to do just that. (These dual-points systems were the predecessor of today’s single-fire system). The dual-point single-fire system was installed in the early ’60s by the Harley dealer network. The factory developed the parts, but would not install them. The dealer had to. Later, an ignition was developed in which each cylinder fires independently of the other. The street name for this type ignition is single fire.

Crane Cams, Dyna, Daytona Twin-Tec and Spyke are companies that offer both single-fire and dual-fire ignitions. H-D itself has developed the single-fire type ignition on today’s TC engines. Each brand of ignition has its advantages and disadvantages. A dual-fire system is the same type that has been around forever and if you select one of these types, the coil that your bike currently has will usually do the job.

A single-fire ignition has the advantage of predictable starting, reduced low-speed vibration, and spark energy focused on individual cylinders. These advantages are distinct and very noticeable. Its drawbacks are the increased initial cost and the requirement that a different type of coil be purchased.

Each manufacture has different specification with options for adjustable advance curves, multi-spark options, increase rev limiters and additional options of selecting from dual-fire and single-fire. Once they are set up and timed correctly they are truly set.

So there you have it.  We’ve given you a little history lesson and a little food for thought when it comes to your ignition system. As always, if you have questions or need assistance picking out an ignition for your motorcycle, don’t hesitate to get in touch with a J&P technician via Live Chat. Or call J&P’s technical support staff at (800) 397-4844.

Comments: 12 Comments | Categorized Under: Tech Tips

Comments (12)

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Great explaination of the differences of the firing. Even I understand now!

I find it simply amazing how the metric riders are so defensive of their rides. Is that why the brand of the bike is not on the tanks w/custom paint jobs, or emblems removed on their stock tanks. Is it because the manufacture has done everything to make the metric look like an HD? I don’t recall ever seeing a Yamaha, Honda, Suzuki, etc inked on the owner. I have owned my share of metrics, but my dream of owning & riding a HD begain when I was 12. No showing off, just ride..130,000 mls & counting. Put your “big girl panties on” and deal with it Stan!

I had run of the mill spark plugs which were copper. Upgraded to platinum coated and it does really improve the start.

Many of us who own Harleys could not care less about showing off. We like them because they are relatively simple to work on and are very reliable if maintained. And you don’t bathe engine parts in clutch disk residue.

There are many riders on the HD message boards with Harleys well into six digits on the odometers (if they would go up that high), so any crap about unreliability is simply BS from the chronically uninformed.

Individual Harleys can break, just as individual Asian bikes can break. I saw a Kawasaki with a broken cam (?) the other day, and tell me some time about how reliable VTX steering neck bearings with plastic races are. Don’t even get me started on how much ti costs to replace the alternator on a Gold Wing.

I own a ´95 FLHR Road King. I wonder what kind of ignition system has it got: a dual o single fire system?
Just for the sake of knowing. Actually whichever it has it runs pretty fine for me.
Thanks for the article very illustrative.

Your 1995 FLHR is Dual fire.

It is a shame you are publishing just harley articles. Some of us are a little wiser, not trying to show of and get a better deal with quailty on metric bikes.

It would seem that the single fire would be the way to go but what is the performance difference between the dual fire and the single fire?

There is no difference I have found on the Dyno. Single fire starts a bit easier, and runs a bit smoother, but is more expensive to set up (requires the use of a special coil). Dual fire has a little more low speed vibration, but is easier to set up as a new system.

If it makes any difference, I run Single Fire on all my personal bikes.

Scott

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