Tech Tips

Welcome to the mysterious world of wrenching. So you weren't born with a silver wrench in your mouth? No idea, how to tell a metric nut from an SAE bolt? No clue about torque settings, drain plugs or hex keys? Don't despair, here's a few basic mini tutorials to keep your sled rolling.

How H-D vehicle identification numbers work, and how to decode them.
To understand vehicle identification numbers (VIN) is crucial when buying an old Harley. It’s the only way to check if the papers belong to the bike and vice versa, and a lot of trouble and heartache can be avoided by doing so.
The VIN is the basis to set out from when shopping for spares and when researching parts in old parts catalogs. As the system has changed a couple of times in the last 117 years, we provide an overview.

Knowing the technical engine data of a Harley-Davidson not only helps with repairs, tuning, or engine overhauls, but also with accurately identifying individual engine variants. Measurements such as bore and stroke, specifications for installation tolerances, and correct displacement assignment are crucial when it comes to spare parts, engine assembly, or selecting compatible components. Our overview lists the dimensions and specifications of popular H-D engines.

Find the fill capacities for the engine, gearbox, primary drive, and fork of your Harley-Davidson model. Our overview shows at a glance how much oil or fluid each component requires - from engine oil to transmission oil and fork oil.

The tire markings on the inner side provide important information about the manufacturer, dimensions, and performance data, and are extremely helpful when selecting the right tire for your Harley-Davidson. There are three commonly used designation systems: inch, metric, and alphanumeric (self-defined term consisting of a combination of letters and numbers). The tables on this page explain these systems.

The tables and articles in this chapter help you correctly identify inch-based threads used on Harley-Davidson motorcycles and compare them with their metric equivalents. They include information on tap drill diameters for internal threads, small thread sizes in the SAE numbering system, as well as SAE pipe threads. This allows you to correctly select and install fasteners and components.

Use this table to easily convert millimeters into fractions of inches or decimal inches.
Convert the fractional number after the hyphen to a decimal, i.e. divide numerator by denominator (see chart) ... 11 by 64 = 0.171875, Replace the zero of the intermediary result with the integer of your basis ... thus 0.171875 becomes 3.171875., To convert in millimeters (centimeters) mulitply this inch-decimal by 25,4 (2,54): 3.171875 x 25,4 = 80,566 mm,

Tables for common Harley-Davidson specifications, including conversions from inches to millimeters, PSI to bar, and other physical quantities. This allows dimensions, fluid capacities, and other physical quantities to be quickly and reliably compared between the US and metric systems.