Bonkers Rev counter on Varitronic

[Raveydavey]

Wired up a Koso rev counter using one of their suggested methods: wrap the sensor wire around the HT lead. However when it runs the revs are really high: around 6 to7k at not much more than tickover. The stator is a Varitronic. Am I seeing the effect of the double spark? There is an option to wire it direct to the CDI but I cant think this would be any different. Any ideas clever people?

[dickie]

The double spark will definitely be doubling what is displayed on the tacho. From the numbers you're giving, it sounds like there is something else at play here though.

Can the Koso be configured for different numbers of cylinders? Many can. If so, I'd start by setting it for twin cylinder operation.

[Raveydavey]

Changed it last night to 2 stroke twin piston, and selected the low sensor setting. It's definitely better. Now the needle waves around like a really knackered speedo: loosely pointing at roughly the revs the engine in running at. I'm suspecting the sensor doesnt like being wrapped around the HT lead. The SIP Speedo (which are made by Koso) on my other bike has the rev sensor plugged in to the lighting circuit at the rectifier end. Might be the way forward?