Buell 1125R - Liquid Fire
No More Potato-Potato. It's Wiener Schnitzel For Buell's Flagship Sportbike, As The 1125R Uses A Liquid-Cooled V-Twin Built By BRP-Rotax In Austria In Place Of The Timeworn Harley-Davidson-Based Engine
Every year we attend a handful of new-bike intros around the world. At these introductions, representatives of the hosting company brief members of the press on the new bike: the highlights of the new model, why those features were implemented and what they mean for performance. Following the briefing, journalists enjoy a day or two riding and evaluating the new bike. Usually, the whole scenario is fairly predictable: Feature A makes part B lighter than it would be otherwise, allowing an increase in revs by C rpm, for example, and it's easy to notice those features when riding the bike. Simple rules to follow. Buell intros are different. But that shouldn't be a surprise, as any of the company's representatives will tell you the whole company is different. Erik Buell essentially makes his own rules. And for 2007, he's completely rewritten the rule book.
After years of insisting that an air-cooled, pushrod 45-degree V-twin is the best engine for the company's sportbikes (er...sportfighters), Buell has unveiled the new 1125R, which features a liquid-cooled, DOHC engine. Why the sudden about-face? Part of the answer lies with customers' expectations: As sportbikes are endowed with ever-increasing power and performance, riders desire even more, and it's likely that the Sportster-derived air-cooled mill finally can't deliver the performance that potential buyers want. The other part of the answer also lies with the customer: While the company has a strong following (especially overseas), Buell hopes to grow it's customer base by attracting riders away from Japanese and European brands. Will it work? That, of course, is the $11,995 question.
The accompanying engine and chassis sidebars go into more detail about the 1125R, but essentially the bike's chassis is very similar to the Firebolt, and housed in that chassis is an all-new engine designed and manufactured by Rotax. Aside from the obvious benefit of more (and more consistent) power, there are other, subtler advantages gained from the switch. Noise and emissions standards are easier met with liquid cooling. The new engine-dubbed the Helicon after the sacred mountain in Greek mythology-is much more compact than the Harley-Davidson-based Thunderstorm motor, improving weight distribution as well as allowing for a longer swingarm. And without the old engine's inherent shaking, there is no need for huge, heavy flywheels nor the elaborate Uniplanar mounting system to reduce vibration.
The all-new Helicon engine was designed by BRP-Rotax in Austria (the same company responsible for the Aprilia Mille line of V-twins), with significant input from Buell engineers. The engines are manufactured and assembled in Austria and delivered complete to Buell's Wisconsin facility. The displacement of 1125cc was chosen to "meet a customer experience specification" rather than fit in a racing category. Stroke is incidentally the same as that of the Mille engine, while the bore is 6mm greater. Compared with the Ducati 1098, the Helicon engine has a 1mm-smaller bore and a slightly longer stroke.
Yes, the switch to liquid cooling does add some weight and complexity, but that is offset by other benefits enough that the 1125R's claimed dry weight is 375 pounds, 20 pounds less than the XB12R. Perhaps more importantly, the company claims real dry weight-that is to say, wet minus fuel, is 421 pounds, just three pounds heavier than we measured our Ducati 1098 at. While claimed peak torque is down slightly from the Firebolt, the new engine has a claimed 146 horsepower, a whopping 43 more than the XB12R. And while the XB motors ran out of breath rather suddenly at 7000 rpm, the new mill runs to 10,500 rpm.
The new bike was introduced to journalists at Laguna Seca, with a one-day street ride followed by a day lapping the spectacular USGP track. The street ride consisted of a 200-mile loop taking in the Pacific Coast Highway, some freeway and various ranch roads through the rolling hills around Monterey.
1125R Engine Tech
A chain drives the intake cam, while a separate gear drive connects to the exhaust cam. Note the use of stick coils, and the offset between the cams-the exhaust cam sits slightly lower than the intake, opening up room on the intake side for a straighter, larger port and saving space on the exhaust side to shorten the motor's overall length.
The 72-degree V angle was chosen to optimize packaging, as it allows the straightest intake path from throttle body to valve without crowding the throttle bodies between the Nikasil-plated cylinders and also minimizes the length of the engine front-to-back. The dry-sump design utilizes a partition in the crankcase to store the oil rather than an external tank (or the swingarm, as used in the XB models).
Rather than use a cush drive in the rear wheel (adding unsprung weight), the 1125R has a "compensated" front sprocket to absorb driveline shock and reduce wear on the belt. As on the XB models, the Goodyear Hibrex belt needs no adjustment or replacement. The belt drive is now on the left side, opposite to the XB's layout, and the new transmission is a six-speed versus five.
The large diaphragm controls the clutch, reducing lever effort and adding a slipper effect by using vacuum to disengage the clutch. Conveniently, engine vacuum is high at idle-reducing lever effort by approximately 20 percent-and also on closed throttle, providing more slip at higher rpm. The setup is similar, if not identical, to the system used on the Aprilia Mille engines. Oil is evacuated from the crankcase through the clutch cover using vacuum, reducing windage losses. The water pump, just above the crankshaft here, incorporates one of the three balance shafts on its gear. A second balancer is seen here just below the crankshaft.
Rather than using a shim-under-bucket layout, the Helicon engine has finger followers. The followers allow adjustment without removing the camshafts, although the 1125R's engine must be lowered to access the front valve cover. This arrangement helps close up the included valve angle to a shallow 14 degrees, in turn making the combustion chamber more compact.
The third balance shaft is located on the rotor side of the engine, just above the crankshaft. Two counterbalancers reduce the inherent primary imbalance of the 72-degree layout, while the third accounts for the rocking couple created by the side-to-side offset of the cylinders (the width of a connecting rod). Ironically, the XB engines have a knife-and-fork connecting-rod setup, with no rocking couple.
Huge 61mm throttle bodies are quite short, with the injectors (one per cylinder) located downstream of the butterflies (also one per cylinder) and aimed almost directly at the intake valve. An elliptical cam varies the throttle actuation for more control at small openings and a shorter throw at larger openings.
1125R Chassis Tech
Like the XB models, the 1125R's swingarm pivots in the rear of the crankcase. But whereas the unbalanced Sportster-based engine of the XBs was installed with a system of dampers and links to reduce vibration, the new bike's balanced mill can be solidly mounted to the frame to reduce complexity and increase stiffness. The frame/fuel tank is larger than previously, with more fuel (5.6 gallons, up from 3.8 gallons) and 57 percent more stiffness. While rake and trail are identical to the Firebolt's numbers, the wheelbase is 2.5 inches longer, with the shorter engine extending swingarm length by even more than that. While the Firebolt and Lightning frames were made in Italy, the 1125R frames are built in Wisconsin.
The updated ZTL2 (Zero Torsional Load) brake has an eight-piston, four-pad caliper developed from the XBRR program. Increased chassis stiffness and more braking power called for a beefier front fork, and the Showa's tube diameter is now 47mm, up from 43mm. Grippy Pirelli Diablo Corsa III tires are standard, and worked great on both the street and track portions of the intro.
The radiators mount to the engine, with flexible brackets and shrouds protecting them in a tip-over. The mounting arrangement frees up space to move the engine as far forward as possible. Internal vanes direct air in from the shroud side and then through the frame and over the engine for additional cooling. This view shows the ram-air inlet, stainless steel brake line, dual exhaust outlets per cylinder, and the O2 sensor used in the closed-loop EFI.
The fuel-in-frame layout opens up more volume for the airbox, just as it does for the Firebolt and Lightning models. But where the XBs breathed through a side-mounted intake, the 1125R has a duct leading to the high-pressure zone under the bottom triple clamp.
In many ways the 1125R is a familiar mount, as the airbox cover, seat, tailsection and clip-ons all look to be Firebolt parts. The ergos are similar, although the seat doesn't feel as sloped up at the rear, and the pegs are quite a bit lower, making the day's ride a notch more comfortable. The fairing and dash are decidedly different from the 'bolt, giving the new bike a completely different style and look from the cockpit. The fairing is much more bulbous and extended, and while the windscreen is no higher, the R has slightly better wind protection than the XB. As well, the dash is updated to a digital speedo and LCD panel for a much fresher look.
While portions of the cockpit may be familiar, the gauge cluster is all new with an easy-to-read analog tachometer and LCD digital speedo. The setup also includes a shift light, lap tiemr, and fuel economy info.
The exhaust note and much of the engine's mechanical sounds are very similar to those of the Aprilia Mille and Tuono, although other aspects of the engine are familiar Buell. As advertised, the pneumatically assisted clutch (now with hydraulic actuation rather than cable) is light-effort when the engine is running. The gearbox shifts smoother than any previous Buell, but is still a bit clunky and agricultural-sounding, especially when compared with an Aprilia or the Ducati 1098's low-effort tranny.
Over the first few tourist-infested miles of PCH, the 1125's engine feels plenty steamy at lower speeds and revs and has little vibration. Power builds quite proportionate with rpm, indicating a flat torque curve that is friendly and fun at a moderate pace. The transmission ratios are widely spaced, with the exception of the fifth-sixth interval, which is quite narrow. First gear gives plenty of pep for leaving a stop, sixth has the engine spinning leisurely on the freeway and a couple of downshifts are necessary for getting by traffic in a hurry.
The Buell's suspension is sportingly firm but quite plush over smaller bumps and roadway markers, and the upgraded ZTL front brake provides plenty of stopping power with a light pull; as before, however, feedback could be better. Steering is somewhat heavy, but thankfully the long-running XB characteristic of requiring a steady force on the inside clip-on to hold a line is largely absent on the 1125. Flipping the new bike from side to side is much easier as a result, and it definitely requires less concentration to ride quickly. Once off the highway and onto a more deserted twisty road where things got more spirited, some faults became apparent. While vibration is not a problem at lower speeds, the footpegs especially shake increasingly with rpm, and above 80 mph in top gear it becomes a distraction. Interestingly, while the XBs have their footrests mounted directly to the frame, the 1125R's are attached to the engine.
My bike overheated quickly on the run up the mountainside-well into the 230-degree range and illuminating the warning light-and it took several miles of idling along before the temperature returned to something normal. The ambient temperature was close to 100 degrees Fahrenheit inland, and every time I started hammering on the engine, the coolant temperature would shoot up. And that heat poured onto my legs and feet, making the ride very uncomfortable as well.
Upon our return to the track, I informed the Buell techs that the bike had overheated. I was told that the bikes were pilot production models and a fix was in the works for production bikes. This would be a common theme over the course of the two days, with every detail that journalists questioned met with a similar answer. For example, the bikes ran rough below 3000 rpm, protesting under acceleration in the higher gears. Other riders mentioned that to Buell reps, and all the bikes were remapped that evening before our track day. Likewise, the 1125's engine braking was somewhat inconsistent, with the bike not losing any speed at some rpm when the throttle was closed; this too would be constantly adjusted over the course of the intro.
At the racetrack, only two bikes had the correct, production fork springs while the rest had springs that were too stiff. The rebound damping circuit in the rear shock had the incorrect needle, giving too much damping that couldn't be adjusted out. And switching from one bike to another revealed more differences than could be accounted for by simple adjustments. Bearing that in mind, it's difficult to form any conclusions from the track portion of the intro, but some characteristics of the bike were clear and consistent.
Foremost, the engine is a huge improvement over the XB motor on the racetrack. The Rotax mill simply has more power everywhere and is not crippled by the wide-ratio five-speed box and low rev ceiling of the Firebolt. The 1125 comes off corners with more strength and carries more speed further in each gear. For track work, the ratios are still slightly wide given the flat torque curve, and I found myself spinning the engine in a lower gear or lugging in a taller gear through more corners than I would have liked.
While the bikes showed no signs of overheating on the track, the ambient temperatures were significantly cooler than the day previously, and coolant temperatures were still in the 210-degree range-warmer than I would have liked if it were a personal track bike. As on the street ride, the footpegs vibrate increasingly with revs, and on some straights the combination of heat and vibration on my feet was almost painful.
Steering effort is lighter on the track than on the street (a point we've raised previously with the Firebolts), but still not as quick as the claimed dry weight and sharp geometry numbers would indicate. Even with the mismatched springs and damping rates, the suspension did a good job of soaking up what few bumps there are on Laguna's new surface. The Buell was quite nervous going over the rise that is Turn 1 and would seriously shake its head arcing through the ripples in Rainey Curve. In smooth turns, the R is solid and stable midcorner, with the Pirelli Diablo Corsa III tires giving excellent grip, but overall handling is quite busy. Whereas the Firebolt could manage without a steering damper, that would be high on my list of add-ons for the more powerful and faster 1125R.
A more in-depth evaluation will have to wait, as final production models are for sure going to change from the bikes we rode. One thing is certain, however: At speeds that taxed the Thunderstorm engine to its absolute limits, the Helicon motor is hardly breaking a sweat. That handily addresses the major concern that Buell's potential customers have when considering a purchase and goes a long way to making the 1125R a much better road and track bike than the Firebolt. Production bikes should be available before the end of the year, and we'll put a bike through the wringer as soon as we can get our hands on a test unit.
An interesting detail: Buell has worked with Sentry Insurance to negotiate lower rates for the 1125R based on the bike's design. For example, small nylon pads protect the sides of the engine in a low-speed tip-over, and the radiator shrouds-sure to be scraped in a crash-protect the frame and are low-cost, easily replaceable parts. Adding these features reduces repair costs, and Sentry takes this into account when calculating premiums for the bike.
Type: Liquid-cooled, DOHC, 72-degreeV-twin, 4 valves/cyl.
Bore x stroke: 103 x 67.5mm
Compression ratio: 12.3:1
Induction: DDFI 3, 61mm throttle bodies
Front tire: 120/70ZR-17 Pirelli Diablo Corsa III
Rear tire: 180/55ZR-17 Pirelli Diablo Corsa III
Rake/trail: 21 deg./3.3 in. (84mm)
Wheelbase: 54.6 in. (1387mm)
Seat height: 30.5 in. (775mm)
Fuel capacity: 5.6 gal. (21L)
Weight: 375 lbs. (170kg) dry