Like the Casa Performance 250 Twin, the most powerful scooter engines don’t have to be the biggest in capacity.

Cristian Mazelli’s latest Vespa endurance racer features for the first time a Crimaz cylinder. Despite only being 132cc it’s already pumping out 47hp on the dyno, and this is at the beginning of the development cycle.

More than that, the scooter features a highly innovative rising-rate linkage system for the rear suspension.

What’s inside?

The engine is built around Quattrini Pro engine casings. These are similar to the normal Quattrini casings we used for our Endurance Race project motor, but they are designed for reversed-cylinder mounting with the exhaust exiting at the front.

At the rear of Quattrini Pro casings is a massive crankcase reedvalve which makes them ideal for the fitment of Kart GP cylinders.

Crimaz wouldn’t let me photograph the inside of his new kit – the CMI Modena Indy – but I got to see inside. From the looks of it, and the power curve visible at the end of our video, you can surmise that it is based closely on Kart technology. 

Karts are one sport where development of the 2-stroke has never ceased. Therefore if you are happy to build engines which make peak power at over 12,000rpm then karting provides a ready source of cylinder and exhaust technology that is ripe for adaption to scooter engines.

The Modena Indy kit uses a revised stud pattern with widely-spaced studs (like the Quattrini M200 kit). These don’t interfere with the internal porting of the cylinder like kits that utilise the Vespa layout. This is all very high-end stuff.

A 39mm VHSB Dellorto feeds the thirsty engine

CMI ‘Modena Indy’ Kit Power Output

The dyno graph we were supplied showed 47hp at 12,400rpm and the engine ran on happily to 14,500rpm. While that sounds mental for the road, it’s pretty common in the kart world.

One advantage of a high-rpm engine is that it only needs a short exhaust system, so Crimaz has made a pipe that turns back, goes over the wheel with the belly under the left sidepanel, and with a muffler that exits sideways near the kickstart lever.

With an ultra-light PVL ignition system running at 18-degrees timing the engine sounds as fearsomely revvy as you might expect.

This exhaust is like Danny Devito: short and fat

Moving Neutral

The next revelation is a totally redesigned gearbox using dished gear cogs to permit a different shift layout. Rather than 1-N-2-3-4, the modestly-named Crimaz ‘New Imperium’ gearbox features a layout of N-1-2-3-4 in order to avoid missed gearshifts from 1^st to 2^nd gear. On the road that will offer very little advantage, but on the track every little helps.

At the moment this gearbox is totally new and not compatible yet with the Quattrini crankcase water pump system, so an electric water pump is required to push coolant to the new under-slung radiator.

Scoop cooling

Indy Frame

 This new engine is housed in Crimaz’ own Indy frame, which is a cast aluminium ‘Vespa-style’ frame specifically intended for racing. Unfortunately for Crimaz, only a few race series permit the use of replacement frames.

The Crimaz Indy frame is undoubtedly a work of art, but should it be legal for racing against modified Vespas?

Crimaz Indy Frame PROS:

• Lighter than a full Vespa frame
• Stiffer than a Vespa chassis
• Can accommodate most engine formats and carb positions
• Adaptable to various suspension systems
• Ready to race off-the-shelf as a shortcut to a competent race bike
• Saves modifying another rare original frame

Crimaz Indy Frame OBJECTIONS:

• The scooter is not a Vespa if you replace the whole chassis
• Some of the fun of building a special Vespa for racing is learning as you go
• If you must buy a replacement frame off-the-shelf to compete near the front then this makes the series more expensive and unfair to those still modifying Vespa frames
• The cost of an Indy frame increases when you take into consideration the bodywork that you must also buy if it is to look like a Vespa
• A replacement frame is not even good for use on the road

This decision on whether or not to permit complete replacement frames varies from country to country and series to series. At present the Indy frames can be used in France, Germany, Austria and Thailand, but not in the main scooter series in the UK, Italy or Spain.

I completely understand competitors’ objections to running an aftermarket chassis in a series meant for Vespa and Lambrettas. Equally, I understand Crimaz’s point that running an ‘Indy’ frame gets you a competent race scooter without the need to cut up another original Vespa.

It’s up to every organisation to make a decision based on the opinions of the people who actually compete in each series.

Stage 6 pit bike monoshock

Central Rising-Rate Monoshock

The big novelty facilitated by the Indy frame and the reverse-carb Quattrini engine casing is the ability to bolt-in a centrally-mounted rear monoshock.

What is Rising-Rate about?

Simply put, suspension works well if the initial travel is soft and responsive to minor road imperfections, however, soft suspension will quickly bottom-out when faced with bigger bumps. The compromise solution is to have a softer rate at the start of the travel but getting progressively stiffer the more it moves in order to resist bottoming out. 

This can be achieved in several ways:

• Fitting two spring rates on a single shock (like Lambretta S1/S2 shocks)
• Laying a rear shock down so the top mount is further forwards than the bottom
• Creating a mechanical linkage system

Linkage systems do have negative aspects too (increased weight, more moving parts to wear etc) but the most important thing is always the quality of the shock and damper.

Crimaz has chosen a Stage 6 pitbike shock which has rebound, compression and preload adjustment. Together with a wide selection of possible mounts for the linkage this rear suspension will be more tuneable than pretty much any other rear suspension for the Vespa engine. 

When can I buy this engine?

Not yet. Crimaz is still testing a prototype of this kit and gearbox, and it can only improve with more miles on the track. So far it’s only done a few laps of Pomposa racetrack on the Adriatic coast

Whether it will be good enough for VespItaly Team to win once again at Magny Cours will very much depend on how this engine and suspension solution develops…

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