Jim Mosher's Performance Indian: Something Old, Something New | DRAWING THE LINE

The year is 1939. In Europe, nations are stumbling into the conflict that will become World War II. In Springfield, MA, flathead V-twin engines roll off the assembly line to be installed in 1940-model Indian Scout military-spec motorcycles. That 45-cubic-inch (750cc) flathead Scout makes about 15 horsepower and might see 70 mph flat out.

Travel forward in time 73 years to August 2012, and two of those ex-military Scout engines sit quietly in the run line at the Bonneville salt flats, framed in a unique vintage racer. The bike has been conceived, designed, and built by Jim Mosher as a flagship for his Indian and vintage specialty shop Performance Indian (_www.performanceindian.com_). It's been three years in the making. The Southern California Timing Association makes the rules, and according to the SCTA class structure, this bike slots into the 1350cc modified-vintage/fuel class. For the SCTA, "vintage" means engines using production cases, cylinders, and heads made before 1955, though each of these can be modified. The modified-vintage class can use modern running gear around those old engine parts.

Although the engines are completely recognizable as Indian Scout hardware, they’ve been completely transformed. From 15 bhp originally they now put out about 66 bhp each for a rear-wheel total of 132 bhp. Cranks use stroked Chief flywheels to increase displacement to 58 cubic inches (950cc), so total displacement is now 1900cc. (The bike slots into the 1350cc class because flatheads get a 33-percent displacement break). Compression ratio is up to more than 7.0:1, from about 4.5:1. Maximum revs rise to about 6500 rpm. Modern dirtbike carburetors supply gasoline, while nitrous oxide injection puts the bike into the “fuel” class. A belt primary drives a five-speed Baker transmission, with chain final drive to a forged rear wheel. The hardtail frame employs clever axle-adjustment plates that allow vertical as well as fore-aft adjustment.

Craig Murray, a veteran vintage roadracer with national titles on his resume, is waiting with the bike in the Bonneville run line, ready to head out on the course. He’s ridden the bike on the road, but the salt is always new, a chameleon surface. He knows how the bike handles and the way the motors deliver power, but nobody can guarantee that these old flatheads will hold together when ridden wide-open, with nitrous. If these engines might turn into hand grenades, where are the pins?

Two runs later Jim and Craig have a record, but it’s also a disappointment. By the end of the second run the front engine is dead, its magneto having come adrift, held on only by the plug wires. There are other problems: electronic ones like a disfunctional tach and data log system, and mechanical ones like sticking valve guides. The new speed record is 128 mph. The frustration is in knowing more is possible.

The next day brings new salt conditions, damp after some rain, and slick. The tach still doesn’t work, so shift points are conservative and revs at top speed an educated guess. The front engine is still being temperamental but hasn’t been damaged, and these runs are more like it. They’ve scored another class record, one now up to 153 mph.

The fastest non-streamlined vintage bike of any class ran 161 mph, so Jim and Craig are just 9 mph short of topping that mark, and are already working toward next year’s events. SCTA-legal fairings for the bike are in the planning stages. There are probably a whole series of records in this bike.

The twin Indian is a true hot-rod, a slice of the past looking to future records. These engines, making four times their designed power, are just as fascinating as an 800-bhp turbo Hayabusa that also makes four times as much as it was designed for. In the beauty of its craftsmanship and intricate packaging, Jim Mosher’s machine is surely the equal of the best bikes and cars that use vintage iron to prove that there’s still life in those old bones.

With tandem-mounted flathead engines in a cutting edge chassis, Jim Mosher’s racer has achieved speeds Indian engineers could only dream of.