The big Rotax four-stroke single found its way into a remarkably diverse range of motorcycles. Applications ranged from Aprilia and KTM trail motorcycles to the Armstrong and Harley-Davidson military machines and later CCM competition and supermoto models, all shared the same Nippon Denso ignition system.

At Rex’s Speed Shop we have been repairing and manufacturing ignition components for these engines for many years. We have now brought that experience together in our updated Rotax 4-Stroke Ignition Troubleshooting Guide, covering the common ignition systems fitted to Rotax 348, 504, 560 & 604 single-cylinder engines.

These engines appeared in everything from competition enduro and motocross machines to military motorcycles. Applications include the Armstrong MT500, Harley-Davidson MT350, various Aprilia, KTM and the legendary CCM604 motorcycles, together with a number of less common specialist and competition machines.

Despite the variety of manufacturers and models, the underlying ignition systems have a great deal in common. This makes understanding exactly which Rotax engine and ignition components are fitted considerably more useful than simply relying on the motorcycle manufacturer’s name.

Our new troubleshooting guide takes owners and technicians through the ignition system methodically, starting with the basic checks before moving on to the HT coil, ignition amplifier, generator windings and trigger system. It also explains how to take meaningful resistance readings and how ambient temperature affects the resistance of the copper windings within the generator.

This is particularly important on machines now several decades old.

Kick starting is a reluctant big single is a miserable and thankless task and one we would like to help you get to the bottom of sooner rather than later. Whether you are investigating an Armstrong MT500 with no spark, an MT350 ignition fault, a CCM604 that is difficult to start, we walk you through a time proven method that has proved its worth.

The new Rex’s Speed Shop Rotax Ignition Troubleshooting Guide brings together the checks, specifications and practical workshop knowledge needed to do exactly that, helping owners keep this fascinating family of Rotax-powered motorcycles running reliably.