Scooterotica

I've ran a Varitronic on a TS1 for years and set it at 24 degrees and never had any issues apart from a stator breaking down and causing a misfire/ stutter at a certain rev. As far as I'm concerned I wouldn't consider anything else apart from maybe genuine Vespa LT coils and pick up with a Kytronic

Same here GT186 at 24 degrees.
Varitronic stator recently replaced after 10 years so can't complain!
Solid piece of kit.

I have set both Varitronic and Casatronic at 21degs tho I was advised to set at 24 (Static/tickover).

Do note that, unlike most bolt-on advance/retard ignition boxes, the Varitronic actually advances slightly from the tickover firing point, then retards at higher RPM. This is done so that the motor is less likely to kick-back when starting and to make it easier to kick-over (not fighting so much advance), then deliver better grunt at low revs, then keep it cooler at higher RPM. Bolt-on boxes simply apply a linear retard function.

http://www.lambretta.co.uk/downloads/vari1.jpg

I run a hi comp motor with a Kytronic set at 28 deg BTDC with the -12 retard and it's so easy to kick over even with a tiny flywheel as they don't advance until 2000 rpm. Definitely recommended for anyone who struggles to kick a motor over.