Tune-Up Tips

Tune-Up your Vintage Vespa

So you’ve got yourself a vintage Lambretta, and you are simply unimpressed with its performance. Its no wonder, our beloved steeds were designed 30+ years ago to cope with the traffic of that time. Motorscooters were originally made to be transport within crowded European cities for short distances, a mandate that did not really require speed. Later on, in the 1960’s, competition between Piaggio and Innocenti, and more importantly, the demand for fast scooters in the English market, pushed innovation towards faster scooters. Nevertheless, a scooter designed for the 1960’s or 1970’s market could stand some improvements to cope with 1990’s road conditions. Luckily for us, there are many performance improvements that are available to help your Lambretta take you into the next millennium. Below is a list of some of the more common things you can do to help your LI/TV/SX Lambretta…

One thing to keep in mind; in scooters, as well as in life - try to keep a balance. If you want your tuned scooter to run well, all things have to be balanced out. A big increase in cc’s requires more gas flow and exhaust output to match. This is even more important in 2-stroke motors, since the motor is lubricated through the gasoline. If there is too little gas getting to your motor, then too little oil is also getting to your motor, and you stand a risk of seizure.

You should also decide what you want your scooter to do before you begin to buy expensive parts to tune it. If you just want to reliably cruise around town, then keep the tuning to a minimum. On the other hand if you want a fire-breathing monster that will haul-ass, but needs to be repaired every week, then go for the TS-1 kit that is ported to look like swiss cheese. Just remember - the more you tune, the lower your reliability and the more it will cost you, both initially, and later for repairs.

Porting :

You can get a decent increase in the performance of you scooter by simply opening up the size of the intake, transfer, and exhaust ports of your existing barrel. This can be done to any barrel, and is measured in “stages.” The first stage is simply matching the intake manifold to the intake port, and the exhaust manifold to the exhaust port, and the degree of cutting goes up from there. Only trust an experienced shop to carry out these modifications, it would be a shame to end up with a ruined barrel due to a cut rate hack job. This is the cheapest way to go, because you don’t need to buy any new components, except maybe new jets for your carburetor.

175 Conversion:

This is perhaps the best conversion for all 125-150cc Lambrettas. It is very reliable, relatively cheap, and will give you more power and top speed. Expect a top speed of around 60-65 mph, and more power all around. To carry out this modification, you can re-bore your existing barrel to take the new piston, or better yet, buy a conversion barrel and piston and just slap it on. The advantage of the conversion barrel is that it comes with better porting to take advantage of the bigger piston. The head will need to be reprofiled to match the new larger bore of the barrel no matter which way you go. You will also need to replace your carb with at least a 20mm item to make use of the extra cc’s. A new exhaust is not necessary, but can give a bit more power.

Gearing:

One thing that makes Lambrettas very interesting to tune is the almost endless possibilities of gear combinations. You can change the size of the primary gear from 15 to 19 teeth (located on the end of crank), the secondary gear from 46 to 48 teeth (located behind the clutch), and all of the gears in the gearbox. When altering the primary or secondary gear, usually you will need to get a longer duplex chain to fit the new gears. Normally changing the primary and secondary gears won’t be necessary, and is only done to really customize a motor to one’s personal taste. The only time it is useful is if you are tuning an LI 125 or 150 motor. Major improvements in power require lower gearing to make use of them, and a 125 gearbox is not very useful on a highly tuned motor. When building a tuned motor, always ask the shop where you are buying your parts if a different gearbox might be necessary.