Project 137 Bis (second part)
A new twin-cylinder engine for Lambretta "Targa Twin 250" has been presented on the 15th and 16th of November at the Motorscambio fair in Novegro (Milano).
Present at the event were Mr. Tino Sacchi, inventor and patron of the project; the engineer Mr. Franco Dell'Acqua, designer and responsible for the technical part and quality check of the project; and Mr. Charlie Edmonds, tester and designer of the exhaust system as well as official rider. Also present, Trevor and Peter from the Cambridge Lambretta Workshop.
The prototype already shown in a definitive form will be equipped with new carburetors and provided with power jet furnished by the Dell'Orto Company.
This engine in its standard version have already 28 bhp each wheel with two carburetors 26mm in diameter and 31 hp and two carburetors 30mm in diameter with air filter, it delivers a good torque enough to be used easily in the city traffic.
The "Targa Twin" shows its power from 3800 rpm, progressively with no shocks or hesitation, reaching 7800 rpm and going easily over it in over-revving.
The Targa Twin can be considered the modern evolution of the experimental twin cylinder engine by Innocenti (project 137) created in only two prototypes now exposed at the Scooter Museum in Rodano and which I had the honor to test in the past.
Originally the twin-cylinder engine was 200 cc with a power estimated around 15/16 hp. Now its power has doubled but still maintains the same style of its predecessor.
The guide lines defined during the planning phase, were followed vigorously and are listed as follows:
- Horizontal twin-cylinder engine (bore/stroke 54x54), front gear, air cooled.
- Tunnel monobloc engine, balanced on silent blocks with single shock absorber.
- Decomposable drive shaft respectful of the original structural principle.
- Assembly with no alteration to the frame or to the inside of the panels, glove compartment, tank, controls, etc.
- Cubic capacity between 200 and 250 cc. Possibility to increase it to 275 cc.
- Scorching acceleration and speed superior to 145 km/h are worthy characteristics of the Lambretta brand with no renounce to good handling and durability under any condition.
I also need to thank the collaborators who followed these rock-like indications; our goals have been reached and even exceeded. In fact with this new engine, the Lambretta turned out to be very easy to drive, moderate in the fuel consumption and at the same time, very generous in the power supply, usable delivery while keeping a contained noise.
Some original technical characteristics allowed reaching first class goals in terms of performances, efficiency and durability:
- Cylinders with four transfer ports, made in Nicasil aluminum and molded in sand are fixed to the block with 8 studs and special allen nuts.
- Central dome-shaped heads with squish band are fixed to cylinders with 6 studs each. This conformation, once abandoned the original studs system, allows a better control of torque and avoids distortions.
- The electric ignition Varitwin 12v 100w allows a quick start and an optimal ignition at any engine speed and a perfect combustion in any condition of usage.
- The twin crank shaft is on three bearing supports. Personally built by the engineer Carlo Mazzucchelli with first class materials, they'll be signed one by one as warranty of great attention.
- Pistons, produced by the Meteor Company, are for their quality and lightness able to ensure a safe running for many kilometers. Two rings 1mm thick are made of chromium plated spheroidal cast iron. Not even the roll cages have been ignored: silver coated and from the kart world, they are for this reason certified up to 14.000 rpm
- The expansion exhaust system, designed and carried out by Mr. Charlie Edmonds, is a "two in one" kind. The exhaust manifold is supported by adjustable mounting brackets, that allows it to accurately centre the bulky silencer in the available space without interferences. Gas welded with a 1,2mm sheet steel, is the best system to have for a two stroke engine. Charlie Edmonds also took care of the final set up.
- The Europlast Company will supply, on demand, a bigger tank and the Ancillotti Superlight saddle.
- Other details enrich the engine like the cowlings built in carbon fibre, while the oil caps are made out of an ergal solid piece.
- Finally, the engine will be equipped with a rear hub from the second series Lambretta, more robust, safer and suitable to new performances.
As soon as possible, when an accurate and definitive carburetion set up will be brought to light, data concerning couple/power/consumption/speed will be communicated.
Thanks to those who believed and contributed to realize this project, a result that many waited for and a clear answer to a few skeptics.
TINO SACCHI
www.lambretta.it
