Truett & Osborn

There is NO Substitute for more cubic inches! Boost your little Flatty up to 54 cui or 900cc respectively and experience the change from a lame duck to an agile pony. These 4.5” stroker flywheels require special stroker pistons which are also available. Recommended for qualified mechanics only because the flywheels need to be balanced and the engine cases and cylinders must be relieved for the rods to clear. The selection includes: flywheels for stock 45” crank pin and connecting rods, flywheels for racing purposes which work with stronger 1957-84 Sportster crankpins and connecting rods,

Of all measures to increase horsepower and torque of your factory engine, stroker flywheels are among the most effective. Boost your stock displacement 61” or 74” Knucklehead, Panhead or Shovelhead up to 84 cui (=1380cc) (@ 3-7/16” bore) and experience arm stretching performance and a significantly increased fun factor. Especially with original engine cases these 4.5” stroker flywheels are the way to go. If any, they require only minor modifications for installation and unlike with machining for Big Bore cylinders cases become not weakened. Consequently, engine life expectancy is near stock. All versions are of Torque Monster type with thick left flywheel as original and require special stroker pistons, which are also available. Manufactured from 80-55-06 ductile iron blanks, which are then heat treated. The 80,000 pound tensile strength blanks undergo an exacting 20-step manufacturing process, utilizing both CNC and conventional precision milling and machining. This insures accurate surfaces, legendary reliability, and excellent „truability“, an absolute necessity when setting up high performance motors to blueprint specifications. With pre-installed and replaceable connecting rod thrust washers, providing increased service-life and restorability. Recommended for qualified mechanics only, because the flywheels need to be balanced and clearances in engine cases need to be checked.

Truett & Osborn Precision Flywheels – the Perfect Upgrade for Worn Originals Worn or warped flywheels pose a frequent and costly challenge during engine overhauls, especially on classic Harley-Davidson V-twin motors. In many cases, replacing them with brand-new Truett & Osborn flywheels is more cost-effective and enhances long-term reliability. Manufactured from durable 80-55-06 ductile steel with tensile strength exceeding 40,000 kg, each set undergoes a meticulous 20-step CNC and conventional machining process. The result: flawlessly flat surfaces and exceptional dimensional stability, making crankshaft centering significantly easier. These flywheels replicate the original design: the left flywheel is thicker than the right (except on JD and 45″ models), and both weight and inertia match OEM specifications to maintain authentic behavior. Delivered unbalanced, these flywheels allow custom balancing with your engine’s rods, pistons, and peripherals. Like the original crankshafts, Truett & Osborn flywheels include wear plates for the connecting rods, enhancing durability and ease of future rebuilding. Perfect for period-correct restorations, performance builds, or as a dependable replacement for worn originals.