Yamaha RD350LC YPVS 31K

Bertie Simmonds
April 25, 2017

Q: Do you know anyone who can check or test CDI units? And what are the obvious symptoms if a CDI unit is faulty?

31K CDI knackered?

A: The usual symptom for a faulty CDI unit is no sparks at all, as opposed to occasional sparks or sparks at the wrong time. Other components in the system include the pulser source and ignition coils, as well as electrical connectors and wires, and one of these is probably more likely to be the culprit. I suggest that you get hold of a copy of either the genuine Yamaha or Haynes workshop manuals as there is a test sequence to follow to determine where the ignition fault lies, and the correct electrical resistance readings you should have.

About the Author

Bertie Simmonds

As a child Bertie (well, Robert back then… blame his sister for the nickname) was exposed to motorcycles thanks to his uncles. They would show up at his house with a lovely lady as pillion throughout the 1970s and 1980s. After a naughty time on field bikes (it’s what we did back then) Bertie passed his test in the early 1990s and became a reporter for MCN in 1995, moving to the sports desk and covering World Superbikes in 1996. With a change to Bike Magazine in 1997, he stayed until 2000 as news, features and road test editor. Moving into PR with Cosworth, Bert was bored with cars and returned to bikes in 2001 with Two Wheels Only, becoming editor in 2002 and leaving to be freelance at the end of 2004. With almost a decade freelancing, Bertie joined Mortons in 2013 and became editor of Classic Motorcycle Mechanics, a post he’s desperately clung to, to this day. And no, he’s never had a pretty girl on the back of his bike.

Share this article