After a rebuild or if your engine is running badly checking your timing is a good idea. On Vespas starting with the Rally 200 and on Lambrettas after the GP200 the ignition system changed from points to electronic ignition. An overview of the principle of this ignition can be found here. This page shows a typical timing procedure on a P200E but the steps can also be used on other electronic ignition bikes.

You'll need:

• A timing gun - usually these run off a separate 12V source (such as a scooter or car battery) and can be bought from most auto parts stores. I don't recommend the type that run off the power in the HT lead as they are not very bright.

If the timing needs to be adjusted you'll also need:

• A flywheel removal tool
• A flywheel holding tool
• A 19mm socket for the flywheel nut
• A large Philips head screwdriver

There is really only one part which can be adjusted in an electronic system and that is the stator plate. Piaggio has engineered all the marks and lines so that it is essentially as simple as aligning these marks. If you need to time the bike to a setting other than stock for tuning purposes, you can use this page to determine TDC and when the motor needs to fire.

Checking the Timing: When you initially rebuild the bike, align the stator with the mark on the crankcase and screw in the three Phillips head screws to reatin it . This mark is typically a raised line and should align with a similar line on the stator. This is the starting point and the stator may have to be adjusted once the timing is checked. Once the motor is back together, connect your timing light to the HT lead and to a battery. Either start the engine or use a 19mm socket with a drive that can be chucked up in a drill. If you use the drill method, remove the spark plug but still leave it attached to the HT lead and the plug threads grounded to the engine casing. This will make turning the engine with the very easy without compression and there will be no danger of damaging the engine through incorrect timing as the plug isn't igniting anything inside the cylinder.

The way a timing light works is similar to a strobe light in a disco. If you were in a very dark room on a trampoline and every time you reached the top of your bounce a strobe light fired, anyone watching you would think you were levitating because they only see the same quick image and not the drop and bounce in between. With the engine either running or turning with a drill the timing gun will quickly flash when the plug fires. Marks (shown below) on the flywheel and either the fan housing or the flywheel should match up under the strobe.

There are two types of flywheels that were used on Vespa P series electronic ignition bikes. The images above show the stock timing marks that can be checked with a timing gun.