Speed's Spotlight: Hot Sparks!

Dealing with fouled spark plugs

harley spark plugs

Speed's Spotlight: Hot Sparks!

The fix the SPP crew serves up here, besides a gentle reminder to not be in such a hurry, will most often be a new set of spark plugs and maybe some fresh wires to go with them.

Words and Photos: Joe Kress

“There goes another one,” Jamie Hanson says, pointing out something he sees a lot. A rider’s just returned to his bike that’s been parked out in front of the Speed’s Performance Plus truck all day. Sitting there for hours on a chilly afternoon it’s now dead cold, and that rider, without so much as a minute’s warm-up time, has taken off with a roar. The problem? Besides barely giving that bike a chance to build oil pressure, bad enough, on a late-model EFI bike like the one just ridden away, Jamie says, that get-on-and-go routine is pretty much a guarantee for fouled spark plugs, black as coal. “The computer’s still in its warm-up mode,” Jamie explains. “It’s like riding off with the choke full on.”

The fix the SPP crew serves up here, besides a gentle reminder to not be in such a hurry, will most often be a new set of spark plugs and maybe some fresh wires to go with them. And for a while now the only plugs the SPP guys use are the NGK Iridiums. “We don’t bother fooling around with anything else,” Jamie says. Yeah, Iridiums cost more, but that Iridium tip on a spark plug is highly durable, delivering a consistently stable spark. You get what you pay for. And when it comes to the wires, Jamie says, it’s always low resistance. Either SPP’s own top-of-the-line sets made up just for them or the Taylors they also keep in stock. “And we've had great success with those Taylors,” he says. The price is right too, at less than $30 a set.

But what about the rest of a Harley’s ignition system, we wondered? Anything to be gained there with some knowledgeable fiddling? “Absolutely,” Jamie answers. “And the more modifications an engine has made to it the more an optimized ignition will offer.” Optimized, in SPP terms, means initial timing and advance curves custom set to the bike. For a fuel-injected engine, the same Power Commander or Power Vision programs usually used to set fuel delivery will also be used to custom tune the ignition. “And you can be just as precise with that advance curve as you were dialing in the fuel,” he says, adding advance where it’s needed or taking it away one degree at a time at 250-rpm increments from idle to redline. Spark setting doesn’t get any closer than that. And with carbureted bikes it’s pretty much the same story, differing only in how you get there. “We use a ton of the Twin Tec ignition modules for that,” Jamie says. “The nose cone versions for the earlier Evo bikes and the plug-in ones for the carbureted Twin Cams.” Head and shoulders above anything OE, these adjustable ignitions allow you to custom-set the rpm limits, the initial timing, the advance curves—the works. “And what’s really cool,” Jamie adds, “is you can also set those ignitions for either single- or dual-fire and for multi-spark fire.” And multi-spark, a continuous series of sparks fired from the advanced timing point until TDC, goes a long way toward reducing plug fouling, especially at idle.

Now, ignition work like this isn’t going to make a night-and-day difference on a mostly stock bike, Jamie points out. “But every little bit helps. It’ll make that bike a lot happier running, cooler running, and smoother riding.” And believe it or not, new plugs and wires alone can pick up anywhere from 3 to 5 horsepower all by itself. The SPP guys have seen it on their dyno. Where that ignition upgrade really comes into its own, though, Jamie explains, is on a motorcycle that’s had some serious engine modifications made. Cam changes, high compression, that sort of thing. And in those situations dialing in the ignition will help reap all the benefits of that other work. Quite often it’ll be the difference between a good-running engine and one that’s not, particularly when that engine’s been assembled with a mismatch of hardware. Not enough cam with too much compression, for instance. In those cases custom dialing the ignition curve is going to be the difference between an engine that’s running pretty good and one that’s pinging like crazy and beating itself to death.

“But either way,” Jamie says with a laugh, “stock or modified, it’s always going to be a lot better if you let that thing warm up first!” Next time the Speed’s team is in your area, stop by and talk ignitions. Maybe even help the SPP folks pick out the riders headed for a set of fouled plugs!

Source: Speed’s Performance Plus

(605) 695-1401 - MN

(605) 695-2272 - SD