Bad Dog 215 is a fuel-injected, sixty-degree air-and-oil-cooled
4-valve DOHC semi-unit V-Twin, displacing 3500 cc or 215 cubic inches.
We expect the motor to develop about 300 ft.lb. of torque at 5000rpm.
and over 300hp. at 6000rpm. The bore-to-stroke ratio is over-square,
with a 6.000" bore and 3.800" stroke. The con rods are several inches
longer than the usual automotive type and run side-by-side on a single
The crank is machined from billet steel and has two bolt-on counterweights.
The cases are billet aluminum, horizontally split, and are fitted with
Chrysler big-block main and rod shell bearings. The drive side has two
main bearings and the timing side uses a single flanged main bearing.
An external multi-stage pump supplies and scavenges five liters of oil,
which passes through a large oil cooler before returning to the oil
tank. Oil jets set into the upper case cool the undersides of the pistons.
The timing side of the crank is keyed to two cam chain sprockets, a
sprocket to drive the oil pump and a timing disk. The crank-mounted
cam chain sprockets turn intermediate sprockets which spin the cams.
The cylinders are machined from aluminum billet with pressed-in iron
liners. The cylinder head will also be machined from an aluminum alloy
with good strength at high temperatures. The head incorporates several
design features to assist cooling.
The valve and port layout is designed to optimize gas flow and increase
Fuel supply is low-pressure electronic sequential port-type injection
with two injectors per cylinder. Injection and spark timing are handled
by a Motec M400 ECM. Scoops on each side of the fuel tank take in air,
which is then filtered before it gets to a plenum between and above
The primary drive will use Harley-style chains, sprockets and clutch.
Production versions of the motor could feature a pair of herringbone
gears instead, but, for now, the chain drive parts are easily available
and should do the job. The transmission has six speeds, using a rotary
shift drum. The primary drive and transmission bolt both to the motor
cases and to each other. The swingarm pivot is part of the transmission
housing. The whole power unit mounts to the frame with a rubber vibration-insulating
system that only allows movement in one plane.
A matching frame for the Bad Dog 215 engine will be constructed from
1.25" x .125" 1020 DOM steel tubing. The top frame tubes are oval section
and the steering neck is 3" x .25" tubing.
The complete power unit, including motor, six speed transmission, primary
drive, fuel injection, ignition, engine management system with software,
sensors, charging system, external oil pump and starter has an anticipated
price of US$40,000.
The cost of the matching frame will be approximately US$3,500.