This is from the NewTronics (formerly Piranha) website.
Q: How do I time up my new ignition system?
Timing your new ignition system is the same as for points - consult your manual.
When timing the engine, you should be out of direct bright light, and when timed up, all covers need to be replaced on the engine before it is taken outside and run, or it will not run correctly. The triggers/pick-ups in the system use infra-red light, and an outside source of light will interfere with them.
When timing a two stroke that has the timing marks near where the triggers are located, the static method should be used, preferably with a dial gauge for accuracy. Using a strobe light can cause false readings, as the strobe will be shining on the triggers. A strobe light is only necessary for engines that have a mechanical advance and retard system and not for 2 strokes, which nearly always fire at the same point throughout the revs.