Big-inch motors are now the factory normal. That Harley 103 and the Screamin’ Eagle 110 both hold out the promise of real performance, too. But, truth be told, these two Big Twins, at least in their as-delivered configurations, are less than awe inspiring. That doesn’t have to be a permanent condition.
Consider the now-standard 103. Not so long ago 103 cubic inches would have been plenty for bike-night bragging rights. Now it’s OE, and brightening the picture even more these bigger-inch engines also got a bump in compression, up to 9.6:1. So far, so good. But the power payoff for all this belies those numbers. The average output pro tuners have seen here, believe it or not, is right around 60 horsepower, give or take. Of course, that’s running through the stock air filter, the stock exhaust system, and with a factory calibrated ECM. If there was ever a motorcycle engine in dire need of a wake-up call, it’s the 103.
The guys at Speed’s Performance Plus have been shaking power out of these motors right from the start. “But rarely do we see a bone-stock 103,” Jamie Hanson tells us. “By the time it gets to us, most guys have already put on an exhaust system and an air filter, so the 103s we see, the ones coming up to our shop at the shows, they’re usually pumping out horsepower in the mid- to high-60s, touching 70 horsepower.” Lots better, but certainly not what you’d expect from an engine with more than 100 cubic inches of displacement.
“But a cam swap makes all the difference here,” Jamie goes on. “It makes these new engines come alive.” The gain on top of those pipes, air filters, and an ECM re-map? Another 20 percent jump in horsepower, at least. That moves the once-anemic 103 up into the 90-plus-horsepower range, with more than 100 lb-ft of torque, a night-and-day difference from that showroom-stock engine. And the cam choice here, thanks to that factory bump in compression, is easy. The 103, and the 110, can handle lots more cam than its predecessor, the 96, and indeed demands it.
But a cam swap makes all the difference here,” Jamie goes on. “It makes these new engines come alive.
“With these engines,” Jamie says, “we’ve been getting great results with cams as tall as a 570, even more. In a 96, with its lower compression ratio, that much cam might make the engine a little lazy on the lower end. But that isn’t the case here. With these bigger cams the 103 still makes nice torque throughout the RPM range and at the top end there’s all that extra horsepower. There’s hardly any of that tradeoff here that you’d have to make with a big cam in an 88- or 96-inch Twin Cam, choosing between low-end torque or top-end power.”
And speaking of tradeoffs, a gear-drive for those new cams, obviously, is the way to bulletproof that timing chest, but it isn’t absolutely necessary. “But knock on wood,” Jamie says, “we’ve found the crankshafts in these 103s to be pretty good, ready to accept a gear-drive for the cams. The most run out we’ve seen so far this season has been 0.004.” And during all of last year, Jamie says, they only had one or two bikes with a crankshaft too far out of whack to switch over to gears. “For those we had to retain the chaindrive,” he says, “but that isn’t all that bad.” Harley’s later-model hydraulic tensioners, Jamie explains, are way better than the older spring-loaded style. “Yes, they take away a little power, compared to gears, and a chain will never be as strong as a gear, but it makes a cam swap lots less expensive and all the cam grinders are offering the choice, gear- or chaindrive.” And according to Harley, those new hydraulic tensioners are supposedly good for 40,000 to 50,000 miles.
Now all this hot rodding we’re talking about here for the 103 and the 110, the pipes, air filters, an ECM re-map, and most importantly, those cams, is nothing new. It’s that all-bolt-on performance tuning standby, the Stage 1+. Only this time there’s some serious displacement to start with, and even a bit of a compression bump. And the payoff, 90-plus horsepower and more than 100 lb-ft of torque isn’t bad. That’s bike-night bragging stuff. Next time the Speed’s Performance team is at a nearby event stop in and ask about all this. They’ll tell you. Better yet, they’ll show you.
Catch up with SPP at these upcoming events:
• Muskegon Bike Time July 20-22
• Sturgis Motorcycle Rally July 31-August 1
Speed’s Performance Plus
(605) 695-1401 – MN
(605) 695-2272 – SD