David Booth takes to the track to find out exactly how many cylinders it takes to make the perfect sporting bike.
Winner takes all
In the automotive world, it's all so easy; the more pistons you have, the sportier the car. Oh, you can futz with the system with a supercharger, turbocharger and, even, in more recent times, one of those new-fangled hybrid electric motors. But, in general, the more connecting rods an engine has, the faster it goes.
Motorcycling is not nearly so simple. When motorcycling was in its infancy, almost all bikes were singles or V-twins, simply because no one figured out how to make a multi- cylinder motorcycle work. The Japanese then showed the motorcycling world how to make the now-classic, across-the-beam, inline four reliable, fast and cheap. For 25 years, it was accepted that four was fast; anything else was slow.
Then Ducati resurfaced as a superbike force and the Italians made popular once again what had become a forgotten engine format. Not quite as historic, but equally as forgotten, the three-cylinder motorcycle engine has also recently been resurrected by Triumph, first as a comfy-cosy, but somewhat flatulent, touring powerplant, then more recently in some seriously firebreathing sportbikes. So, the mystery begins anew: which is the superior sporting motorcycle engine: two, three or four cylinders?
The weapons to be chosen were actually determined by their popularity during previous testing. Triumph's Street Triple R made the grade because its supersports cousin - the Daytona 675 - won our track shootout last year. The Buell 1125CR made an appearance because a) we didn't know they were going out of business and b) because it was a new take on a format we liked. The choice of BMW's K 1300 R was the least obvious choice, until you realise that BMW - yes BMW - makes the fastest, more powerful naked bike on the planet.
Indeed, the BMW proved two things, at least one of the them obvious. The first is that huge amounts of power are massively entertaining. Tip-toe the 173hp BMW through Shannonville Motorsport Park's tightest hairpin, then hammer the throttle and the K 1300 R launches down the back straight like all the hounds of Hades. By the end of the straight, you can see 250kph on the speedo, assuming you are a) brave enough to keep the throttle pinned long past the braking point and b) stupid enough to be looking at the gauges when you are doing this.
Foolish or no, that phenomenal turn of speed illustrates one important fact - all things being equal, four-cylinder engines produce more top-end power than their two- and three-cylinder variants. It's a simple matter of valve area. Four-bangers can pack more of it in for a given displacement than can twins or triples, so for the same displacement and state-of-tune, a four will always be more powerful.
Of course, power is not everything, and straights are the least challenging part of any racetrack. Serious speed is judged by how fast you can get around corners. The bottom line is that the BMW, despite its heft, managed this portion of the test quite well, though initially it looked like it was going to be the veritable porpoise out of water. Our first two testers were sent out onto the track with the company's new ESA adjustable suspension set to its softest setting. It wobbled around like the proverbial water buffalo on roller skates. Anything that looked like a corner was a cause for panic. Even from the sidelines, it looked like the entire machine was quaking in fear.
Then we discovered the "track" setting and all was well. No, it wasn't transformed into a grid-ready MotoGP machine, but the Beemer became competent enough that a few of us started pushing it hard enough to boil the brake fluid. For something so large, it really does heel over well, as long as you've got the suspension in the right setting. Which is something the Triumph hardly requires. As delivered, the Street Triple R was suspended similarly softly. But while the soft springing did limit the available ground clearance in cornering, it didn't really affect handling all that much. The basic ingredients of the Triumph's chassis - light weight, short wheelbase, ideal rake and trail - are such that, even with the dampers on full soft, the little triple scooted around the race track with ease.
Of course, after we did fool with its suspenders (the "R" version gets fully-adjustable suspension, fore and aft, compared with the standard Street Triple), it turned that much sharper, the steering felt directly wired to our brain. Triumph may have softened the suspension of the Street Triple versus its Daytona sibling in respect to its street orientation, but the basic goodness of the chassis has not been lost. And the Triumph could be braked hard lap after lap without doing anything foolish like turning the brake fluid the colour of well-steeped tea.
Of course, that's because the Street Triple wasn't going anywhere near as fast as the big Beemer. Yes, it was lighter. And, yes, it revs higher. But, at roughly half the displacement of the German broadsword and with 69 less horsepower (105), there was no way it could even remotely play in the K 1300 R's wake. That said, there's lots of good things to say about Triumph's 675cc engine. For one thing, thanks to its three-cylinder format, the 675 is significantly torquier than a comparable Japanese four-cylinder 600. Where an inline four might not start making serious power until 10,000 rpm, the Triumph has decent torque as low as 6,000rpm. In the middleweight category, that passes for stump-pulling, low-end grunt.
Low-end torque is something that the Buell 1125 has in spades. Say what you will about the now-defunct American sportbike company - questionable reliability, odd-duck styling, etc. - the 146hp, Rotax-built 1,125cc V-twin is a gem. Though it revs with ease to 9,500rpm - high by big twin standards, but nothing compared with the 12,000rpm the Triumph spins - once above 4,000rpm, all that torque makes shifting superfluous.
And like all V-twins, it's not only the power that it makes but how it makes power that sets the Buell apart from its rivals. Gas it up at low speed and the engine doesn't so much vibrate as quake, seemingly shuddering in anticipation of the great illegality of the speed upon which you are about to embark. At higher rpm, the rumble becomes more insistent (the Rotax engine uses a 72-degree angle between cylinders rather than the perfectly-balanced, vibration-quelling 90 degrees of Ducati's trademark V-twin), but never objectionable like the pounding of big-inch, solidly-mounted Harleys or the frenzied buzzing of some inline fours. If you're looking for character, V-twins in general and the Buell 1125, in particular, deliver.
The CR also handles well if a little oddly. Sporting V-twins have been rearward-based sportbikes, steered with the rear wheel via the throttle as much as the front. Stable in the extreme, they are generally not the sharpest steering bikes on the track. The Buell, on the other hand, places even more emphasis on the front tyre than many Japanese fours. Indeed, with the 1125CR's standard clubman handlebar, it feels like your head is directly over the front axle. It takes some getting used to compared with the laid-back riding positions of the BMW and Triumph, but it does work well at the track. As well, Buell does (or, more accurately, did) offer an optional, higher "superbike" bar to make the CR more comfortable for the street.
Answering which is the best bike or even which engine is superior to others is as difficult a comparison as I've ever attempted. The only definite is that BMW's size, comfort and incredible power make it an ideal streetbike - if the road isn't too twisty. Then the Triumph's lightweight handling and manageable motor make it the easiest bike of the trio to ride. That it is comfortable and even tempered just makes it all the more versatile.
As for the Buell, as much as it performed surprisingly well, it simply doesn't matter any more. By the time you read this, all the company's remaining stock will have been blown out at ridiculously low prices. And there will be one less sporting V-twin for us to chose from. As for the most desirable type of engine, the four simply makes the most power, the twin the most effective low-end torque and the triple neatly splits the two. In the end, that's why the Triumph, for the second year in a row, won our track shoot-out. It doesn't matter whether it's in naked bike or supersports guise, Triumph's 675cc triple is a stonker. email@example.com