NotTaR of small Gasoline Engines and Rotary Lawn Mowers : Capacitor discharge ignitions systems   
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Capacitor discharge ignitions systems

(From: Matthias Meerwein (mmerwei@eis.k8.rt.bosch.de).)

I once fixed a CDI unit for a 3-cylinder Evinrude 2-stroke outboard motor. The storage capacitor (1 uF, 400VDC) had a short. Quite simple to replace, but digging the PCB out of the silicone RTV sealing compound inside the ignition box was a real pain! But considering that Evinrude charges real big bucks (about 800 DM = 500$) for the ignition box, it was worth the effort. Another possible cause of failure of the CDI are the SCRs. Also, check the charging and trigger windings as well as the cables and connections.