QT50 weak spark

1979 QT50 Yamahopper weak spark. Same results with various (new) spark plugs and coils. What is the correct exciter coil voltage output prior to connection to CDI and after the CDI but ahead of the primary coil?

Re: QT50 weak spark

If you don't have it, the QT50 Shop Manual is HERE break>

Some CDI-related info is spread throughout it.. a couple diagnostic CDI tests.. ignition coil tests.

The wiring diagram at the end would come in handy when tracing wires for general faults.. loose or corroded contacts or connections.. some insulation worn through or similar.. perhaps between the CDI and the pulse generator, ignition coil, ignition switch... and from CDI to exciter coil. .. Of course good grounds are important..

Hopefully, and since you got a weak spark instead of zero-spark, it will turn out to be wiring trouble..

Re: QT50 weak spark

The manual gives limited test specs for the ignition system (pulser coil and magneto charge coil resistance and spark plug gap, all of which have been tested). After that it's pretty much been commom sense. Check all terminals for clean tight connections. Verify ground condition. If anyone has any test data to share, I would appreciate it. If anyone knows of other Yamaha model ignition systems of the era which might be similar, I would appreciate that info as well.

Re: QT50 weak spark

my guess on the coil the first prymary should be 12volts the secondary should be around 15,000 thats my guess i'm not shure

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