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Yamaha DT 175 Ignition

After problems with the Jaycar kit we went for a complete ignition system from a Yamaha DT 175. That is flywheel, stator and blackbox. We'll get the Jaycar kit working eventually, but this will get us going.

The ignition system worked for the test run. Now we have sent it off to Small Coil Rewinds in Geelong http://smallcoilrewinds.com.au/ to get a complete health check. They will be able to tell us if it is 100% OK for what we are using it for, apparently older flywheels are no good for high RPM and their electrical capabilities (i.e. lights) are poor.

The Small Coil Rewinds test showed that the ignition system only works in one direction, anti-clockwise and the Vespa engine runs clockwise (looking at it from the flywheel side). The symptom of this was the engine would start fine but would not rev out. Having tried two carbs with the same result it is what we suspected (hence the test being done).

The cause was the pulser coil which charges the hall effect sensor to generate a pulse. Since it was running in the wrong direction as the revs went up it’s charge went down to a point where sparking stopped completely.

The solution was to rewind the pulser coil for clockwise rotation and that fixed the problem. At $150 to do the rewind though it is an expensive fix.


Yahama DT 175 ignition systems are not suited for Vespa conversions. It can be done, but we have spent as much time and money adapting it to suit, as it would cost to get a brand new, multipurpose ignition system. The unit cost $385 + $150 for clockwise conversion = $535 (plus we spent ~$100 on testing/postage etc). It would have been better to find a new system for $600 and get far superior results without the hassle.

Addional Notes

 Battery and Lights can be powered from both the Green and Yellow wires. A didioe is needed for the battery or a regulator/rectifier (a Suzuki DR250 has one that would suit).

Paul McIntosh,
Mar 25, 2015, 12:10 AM