Inside Indian’s King of the Baggers V-twin

Inside Indian’s King of the Baggers V-twin


Kevin Cameron has been writing about motorcycles for nearly 50 years, first for <em>Cycle magazine</em> and, since 1992, for <em>Cycle World</em>.

Kevin Cameron has been writing about bikes for almost 50 years, first for <em>Cycle journal</em> and, since 1992, for <em>Cycle World</em>. (Robert Martin/)

Indian’s “Challenger” went 180 mph at Daytona this 12 months. That’s 10–12 mph quicker than a 12 months in the past. Issues are heating up quick on this class, which has turn into American manufacturing unit racing. At MotoAmerica’s Laguna Seca nationwide on the weekend of July 10, the highest Bagger lapped faster than Eddie Lawson did on Yamaha’s fearsome two-stroke YZR500 within the 1988 US Grand Prix.

This stuns and surprises us, making this MotoAmerica’s hottest class. It’s the very last thing we count on from heavy, long-wheelbase bikes designed for cozy interstate touring or chugging to Sunday membership breakfasts. However we like to be stunned.

Indian Motorcycle’s race Challenger may be long and heavy, but anyone who has witnessed MotoAmerica’s King of the Baggers racing knows they are anything but slow and boring.

Indian Bike’s race Challenger could also be lengthy and heavy, however anybody who has witnessed MotoAmerica’s King of the Baggers racing is aware of they’re something however gradual and boring. (Brian J. Nelson/Indian Bike/)

Indian’s riders in each KOTB and Tremendous Hooligan courses are present class champion Tyler O’Hara and “the person who’s ridden every part,” improvement specialist Jeremy McWilliams.

Early this spring I attended Harley-Davidson’s pre-Daytona baggers race team test at Podium Membership raceway, southeast of Phoenix, Arizona, to see the brand new racing class. Then I used to be invited by its nice rival, Indian, to MotoAmerica’s Laguna Seca nationwide close to Monterey, California.

There, in Baggers Race 1 on Saturday, I noticed O’Hara and H-D’s Kyle Wyman carve one another up in shut quarters, flicking (Sure! Flicking!) down Laguna’s well-known Corkscrew, then each dropping the entrance getting into flip 11, giving the win to Hayden Gillim on a Vance & Hines H-D. O’Hara in some way righted his 620-pound machine and restarted rapidly sufficient to complete fourth!

Associated: Diesels

The 2 constructing blocks of that 180 mph Daytona velocity are mighty acceleration off the chicane and the facility to power the obligatory 29-inch-wide entrance fairing by way of the resisting air (sportbike fairings are 19–21 inches large). Acceleration? As a result of these bikes have large V-twin engines (Indian’s liquid-cooled Challenger 60-degree V-twin is 108ci/1,825cc) and long wheelbases over 65 inches, they’re like 2022 MotoGP bikes with their variable ride height systems on minimal. Being lengthy and low turns each into dragsters. I used to be advised that on sure tracks the Baggers obtain faster sector accelerations than Superbikes.

Why the 60-degree vee angle, when conventional Indians had 42 levels? As such large-bore pistons strategy backside heart (BDC) the vee angle have to be giant sufficient to forestall skirt-to-skirt clashing.

I had an extended dialog with S&S Chief Engineer Jeff Bailey, who’s supervising engine improvement (and as I’d quickly see, pitching in as a line mechanic when wanted). After I repeated what’s usually stated concerning the class, that horsepower is someplace between 155 and 165, he stated, “Extra.”

Extra To Come

If we think about that “extra” is 170, we are able to mix that with the 7,700 rpm rev restrict MotoAmerica offers Indian to search out that this modified engine breathes and burns effectively sufficient to realize a 162 psi stroke-averaged web combustion strain (aka “BMEP,” for brake imply efficient strain). That quantity, about 80 % of what’s achieved in MotoGP or World Supers, signifies that this engine is at an honest however reasonable degree of improvement, implying extra to come back.

Operating this engine to 7,700 rpm with its almost 4-inch stroke (96.5mm) leads to a mean piston velocity of 4,880 ft per minute and a peak piston acceleration of 4,020 G. Examine the latter determine with the 7,000 G frequently achieved in redlined 600 Supersport engines, or with the 11,000 G in MotoGP engines at 18,000 rpm.

Harley-Davidson’s bigger 131-inch engine is given a rev restrict of seven,000. Earlier than higher rpm limits have been set, engines have been wrecked by over-revving however reliability now appears strong. Though inventory Challenger bore is 108mm, for this class it’s 110mm, giving a 112ci displacement.

“More” than 165 hp is being produced by Indian’s 112ci V-twin used in the KOTB Challenger.

“Extra” than 165 hp is being produced by Indian’s 112ci V-twin used within the KOTB Challenger. (Brian J. Nelson/Indian Bike/)

Sitting to 1 facet in Indian’s work space was a 9-foot-long wheeled engine cupboard containing two fresh-off-the-dyno engines, totally dressed and prepared to be used. At one finish of the cupboard was a set of handlebars with a hand brake.

Examine Indian’s engine with Chevy’s famed 427 V-8, whose dimensions have been a near-identical 108 x 95.5mm. If the KOTB-modified Indian makes 170 hp, 4 of them mixed right into a V-8 would make a perky 680 hp.

Consumption System

On inventory Challenger engines there are two vertical consumption pipes whose oval cross part is equal to 2 52mm spherical holes. Consumption space was restricted by the part of the forged primary body beam immediately above the cylinder heads however the modified engine wanted extra air. The workforce elected to bypass the body beam by making a CNC-ported and additive-manufactured proper angle bend served by an enormous 78mm throttle physique on the best facet. Regardless of losses probably related to the bend, this gained 10 or extra horsepower.

A massive air filter feeds a 78mm throttle body.

An enormous air filter feeds a 78mm throttle physique. (Brian J. Nelson/Indian Bike/)

Growth is all the time “triaged”: Early within the course of, it’s the large objects providing giant positive factors that get tackled first. Because the challenge matures, the main target can shift to smaller issues. That is an thrilling time, because the expertise is visibly altering from race to race.

Cam lift and timings will not be regulated on this class, so when these engines are began they sound like V-8s with lengthy cams. They ka-thump ka-thump till warmup evaporates extra of the injected gasoline, bringing within the second “voice.”


As a result of this can be a fashionable all-plain-bearing engine, its life relies upon upon dependable supply of air-free strong oil one hundred pc of the time (unhealthy issues occur when air will get into plain bearings). However being initially designed for the low mounting place of a touring engine, it was not designed with a deep sump as discovered on Superbikes. Bailey advised me there’s a cavity behind the crankshaft into which the scavenge oil is pumped, assuring that the strain pump’s consumption will stay submerged.

Inside Elements

As in sportbike engines, Challenger’s crankshaft is a one-piece forging having a single crankpin carrying the 2 connecting rods facet by facet somewhat than in a single airplane in fork-and-blade style. For that reason its separate Nikasil-plated cylinders are offset by the thickness of 1 rod.

Primary drive from crank to gearbox is by gear, and drive to the rear wheel is by an S&S chain conversion.

Power to the rear wheel is delivered by an S&S chain conversion.

Energy to the rear wheel is delivered by an S&S chain conversion. (Brian J. Nelson/Indian Bike/)

In early improvement it was discovered that the crankshaft flung off too little oil to ensure gearbox lubrication, so oil jets are offered (there are additionally piston-cooling oil jets). Just like the two-speed Indians that completed 1-2-3 on the 1911 Isle of Man TT, this six-speed gearbox is shifted by mild dog-rings somewhat than by sliding the substantial gears themselves (one key to fast shifting is to scale back the overall mass that the rider should transfer when altering gear).

Chains drive single overhead cams in every head, initially working four valves per cylinder by forked rockers carrying compact hydraulic clearance adjusters. S&S present billet rockers with mechanical lash adjustment, eliminating the mass (and a doable “pump-up” rpm restrict) of the hydraulics.

Shaping the Torque Curve

When this engine was initially conceived its torque curve was deliberate to be “rainbow-shaped”—emphasizing midrange acceleration important for on-ramps and passing. That is in distinction to what was lengthy conventional for such bikes—the “lean-to” torque curve of older two-valve big-inchers—with peak torque on the backside, lowering as engine velocity climbs, and eventually wheezing out approaching 5,000 rpm.

As with all fashionable engine, Challenger’s torque curve shaping is achieved by a mix of port and valve sizes (in what rpm vary will the consumption velocity finest for cylinder filling happen?) plus intake port downdraft angle (how will the kinetic vitality of the consumption stream be divided between the 2 duties of cylinder filling and the technology of combustion-accelerating tumble motion?).

Compression and Head Temperature

Cylinder heads on Indian’s KOTB engines are CNC-ported. Inventory compression ratio of 11-to-1 displays the worth of liquid-cooling, however as a result of the competing 131-inch pushrod Harley circulates cooled oil between its paired exhaust valves, it most likely doesn’t undergo as a lot from excessive head temperature as a pure air-cooled. Compression ratio might due to this fact not be that completely different between the rivals. Most torque is achieved by operating the very best compression ratio doable with out knock on the gasoline offered.

Tyler O’Hara flicking the Challenger through the bottom of Laguna Seca’s famed Corkscrew.

Tyler O’Hara flicking the Challenger by way of the underside of Laguna Seca’s famed Corkscrew. (Brian J. Nelson/Indian Bike/)

The gasoline on this case is VP’s T4, characterised as a pour-in substitute for pump gasoline. It’s lead-and-ethanol-free however does comprise the oxygenate MTBE.

Exhaust System

The exhaust headers start with additive-manufactured stainless items becoming a member of the pinnacle ports to cut-and-welded head pipes that merge into a big high-mounted and horizontal collector. Every cylinder has its personal oxygen sensor, permitting it to be tuned as a “separate engine,” with its personal fuel and spark maps. The massive exhaust collector introduced necessary positive factors. As a result of the engine is large and initially mounted fairly low, it’s troublesome to rearrange for equal-length header tubes and nonetheless stow the collector underneath the right-hand footpeg. Once more, as a result of this engine was born to tour, it was designed “backward”—with the compromise falling on the exhaust system (within the type of sharply curved exhaust ports) somewhat than on the chassis.

On Friday I realized that the engines had just a few new elements on them not tried earlier than, however they have been solely an ignition rotor cowl and first cowl, each in low profile for cornering clearance.

Old and new tech—and cut-and-weld and additive manufacturing—is used to create the Challenger’s massive exhaust system.

Previous and new tech—and cut-and-weld and additive manufacturing—is used to create the Challenger’s large exhaust system. (Brian J. Nelson/Indian Bike/)

Tyler O’Hara’s crew chief Al Ludington (who was at American Honda Racing within the Miguel Duhamel years) stated the riders sometimes use 5 of the six transmission speeds: when you ignore first, the ratio of second to sixth resembles a correct roadrace trans. However from first to second there’s a whopping 47 % drop in engine rpm!

The weekend confirmed that Indian actually has aggressive energy however that Harley might in the meanwhile have extra refined management over theirs. Ludington summed up by saying, “On a transparent observe we are able to do the lap instances, however in a race there might be one other bike blocking you.” He famous that nook exit and acceleration are already good. The current issues are in braking and nook entry. He additionally stated, “The bike responds in a different way to the rider in right- and left-handed corners.”

When a motorbike is capably ridden close to its grip limits, small enhancements in engine throttle connection and smoothness can have giant results. Riders on the 2023 MotoGP Ducati converse of such enhancements over the earlier 12 months’s software program. In racing, time, funding, and sources are all the time in disaster. All the things is a race—winter improvement, spring testing, and each apply in season.

Take note of this racing class as a result of it has the total consideration of main American companies. It’s a fast-advancing demo of all of the strategies of racing improvement and rider versatility being utilized to a category of bike nobody ever imagined on a racetrack.



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