2000 yamaha warrior 350?

Question

Quad has suddenly lost spark. Starter cranks fine. All the lights work. Is it likely the ignition coil or does anyone know a common cause for this problem? Battery is brand new and strong.

Answer 1

Replace the spark plug first, then the cap.  If this doesn't work, then I'd pop the sidecover and check the stator.  

Sometimes these will get moisture and condensation which will build up bad enough to keep the contact from working.

After that, check all wiring for cracks or worn spots.  Check that ground wires are properly connected and aren't corroded.

If these aren't the problem, then replace the coil.  In most cases, a bad CDI will have 'issues' before it finally fails - the quad will go for months acting like it's got jetting problems, or dying when it's hot, then starting fine once it cools down.  If the quad didn't have any of these symptoms, then it's not the CDI.