There is a howling buzz like someone has just kicked a nest of turbo-charged hornets. Lauro disappears into the distance like his Vespa is on a taut bungee cord strung from a building I can barely see. It is not natural for scooters to do that. This is weird science.
This is Falc weird science. In an increasingly commercial world it is such a pleasure to mix with people who do things for reasons of passion. You only have to look at Lauro’s hands to know that he loves 2-stroke engines and particularly Vespas.
It’s always a pleasure to visit Lauro and Anna from Falc. They have a relaxed attitude to the shit that life can throw at you. My previous visit was not long after a massive earthquake hit their region of Italy and effectively cracked Lauro’s ancient farmhouse in two. At the time his kids were sleeping in a camper-van in the garden.
This time when I return, Lauro and Anna have built a beautiful wooden house in the garden for the ever-expanding family to live in. They are still in discussions with the council about possibilities to renovate their ancient farmhouse, but in the mean time work takes place in several buildings in the garden.
From one of the sheds Lauro pulls out a mean-looking stretched Vespa decorated not in pink like his famous sprinter, but matt black as a statement of evil intent. I’ve crossed paths with this scooter before, but at the time it wasn’t running. Now it is.
The engine is half heavily-modified Piaggio casing, half Falc casing. On top sits a water-cooled cylinder that Lauro originally designed for his 125cc Grand Prix hydroplane. Only it wasn’t powerful enough in the boat, so Lauro has bored and stroked it to increase the capacity. Last time I visited it was a 175, now it is 181cc with a 64mm single ring piston and 56.5mm stroke crankshaft. It’s about as sensible as Morris Dancing. In a mine-field.
At the rear sits a flat-topped PMT tyre with lower inflation pressure than Chris Evans’ ego and far more grip on reality. The motor is reed-fed through a baby-eating, rear facing 41mm Dellorto carb.
Previously the scooter’s thumb-controlled sequential gearchange system was controlled by compressed air, but this has been simplified to mechanical operation. At the moment Lauro still has to back off the throttle to change cogs, but he has in mind an electro-mechanical system with ignition interruption. In theory that should save around 0.2 seconds for the two shifts required to cover 200 metres because he can keep the throttle to the stop. It takes balls like Space Hoppers to keep the throttle pinned when even a stretched Vespa chassis wants to somersault.
Lauro fires the Vespa into the distance one more time for good measure. The noise is like pure distilled screams of demons, amplified for your sadistic pleasure. It is both entertaining and scary at the same time.
“The clutch is finished”, explains Lauro with a smile. When this engine made 52hp the clutch would last a whole meeting, but now at 58hp output it barely lasts three launches. The problem is not the power, but ‘la copia’ – the torque – which is too much for such small components to handle. Even the gears want to weld themselves together at this sort of output.
Back to the shed
With the evil sprinter safely returned to its cage, Lauro gives me a private tour of his workshop to show me a few goodies. He uses his own Falc flywheel side casing but he’s still working on the mould for the other half of his own smallframe engine.
Given that there are so many alternative options now (Quattrini, Pinasco and BSG etc all have casings in production), is it still worth Falc making a smallframe casing?
Lauro believes it is – he plans to sand cast and with several different internal forms he can make a number of different variants with rotary, cylinder or crankcase reed induction.
Polini Cup engine
He pulls a motor off the shelf for demonstration purposes. It is the one his rider uses in the Polini Cup. This class is restricted to a 135cc engine with a single exhaust port. Previously the regulations specified a 19mm carb and in that format it still made 25hp! Now with only a 24mm carb his one makes 30hp after 6 years of development and has clocked 163kmh (101mph) by GPS. This is around 8kmh faster than Polini’s own scooters for the class, however Polini still win due to having Grand Prix-quality riders on board their Vespas. Lauro shrugs his shoulders.
Lauro’s motor uses a plain Parmakit ignition with his own Falc fan. He also uses his own gearbox with interchangeable 3rd and 4th gears. For each circuit he had developed a combination of primary drive and higher gears to suit the stock 1st and 2nd gears.
One thing I notice is that his engine runs a reversed cylinder set-up with the exhaust port aiming down and forward. I wonder why he’s chosen that route but the explanation is interesting.
According to Lauro there is a different power output available with a reversed cylinder: less bottom end power but more power at high rpm. The difference is all to do with cooling. Conventional wisdom is that you should aim the cool air from the fan at the exhaust port to maximise cooling potential on the hottest side of cylinder. However, doing so means that the other side of the cylinder – where the transfers are – only receives air which has already been warmed by the exhaust side. Over the course of a race, with a conventional cylinder layout, temperatures build in the transfer area, affecting and raising pressures until less fresh gas can be accommodated in the crankcase with each revolution.
With barrel reversed and the cold air aimed at the transfer side of the cylinder first it takes much longer for the cylinder and casing to over-heat, thus parasitic power loses are reduced.
“With the conventional layout maximum power would be 28hp but after 5 minutes at full power it would drop to 25hp”, explains Lauro.
“With reverse cylinder the transfers are being cooled so full power is 30hp but after 5 minutes racing it has only dropped to 28 or 29hp. The performance is more stable in the race.”
The difference between discussing tuning theories with people on forums and actually talking to someone like Lauro is a certainty that he’s tested all this and knows exactly what he’s talking about. When it comes to 2-stroke tuning, genius often comes with a dodgy haircut and dirty fingers. Don’t trust a tuner with clean fingernails any more than you’d trust a skinny chef…
Words and photos: Sticky – Video: Christiaan & Sticky