72bhp Lambretta Sleeper: David Krayem’s Stretched SX150

From a humble Series 2 Lambretta in 1968 to a collection of classics today, David Krayem’s return to the marque has gone well beyond nostalgia. His latest SX150 may look fairly standard at first glance, but with a stretched frame and a heavily developed 270cc Casa SSR engine producing 72bhp, this is one Lambretta pushing the limits of both performance and belief. Stu Owen reports…

It’s a familiar story: someone owns a Lambretta briefly, moves on, then finds themselves drawn back decades later. That says plenty about the strange pull of the humble little two-stroke from Milan. For David Krayem, his first Lambretta was bought out of necessity and owned only for a short time, but the seed had been planted. Years later, that early connection resurfaced, not as a passing interest, but as a full-blown collection.

David started with an Li150 Series 2 in 1968, and as a teenager, having just entered the world of employment, it was the ideal choice for getting to work. That’s all it was used for, though, and once funds for a car permitted, the Lambretta was surplus to requirements, and for now, his Lambretta journey had come to an end. As time went by, it became nothing more than a faded memory; however, as it is for so many, those stirring emotions of a misspent Lambretta youth can quickly resurface. For David, that was seeing a group of riders in his hometown of Tetbury, all on Lambrettas, which made an immediate impact.

Mix and Match

David’s chance encounter with the Lambretta riders happened a decade ago and abruptly ended his long sabbatical with the Italian marque. It quickly became a huge catching-up exercise, amassing many different models, with fifteen at one point. Slowly, that figure was trimmed, and currently the total stands at eight, but it’s an eclectic mix. There are some tame machines, such as a model D and an LD, mixed in with a couple of early Li models, all in standard trim. At the opposite end of the spectrum are the later TV, SX, and GP models, and though more powerful in standard trim, David has taken them way beyond that.

It’s commonplace for those with a collection of Lambretta to mix them with standard and tuned engines. However, in this case, while a couple are mildly tuned, the others are completely off the scale. David can be classed as a speed freak, owning high-powered motorcycles and running a GT championship team with cars in excess of 600bhp. While the Lambretta might not be at that level, the right combination of power-to-weight ratio can certainly turn a few heads in terms of performance. However, creating a Lambretta with this level of performance takes some doing, and there are plenty of obstacles to overcome, which David found out.

Visual impact

The first thing you notice about all of David’s tuned Lambrettas is that from the outside, they look relatively standard. Of course, there are telltale signs, such as a big expansion pipe sticking out of the side and heavily upgraded suspension and brakes at the front. There isn’t much chance of hiding or disguising those bits, but they’re all that’s on offer as clues. There are no flashy paint jobs or anything like that; no race numbers or brand logos either. Instead, standard colours perfect the art of the street sleeper style. While the turquoise GP125 packs a punch with its SS200 engine (40bhp), it’s the SX150 that steals the show.

Finished in a factory green paint scheme, it may look tame in its appearance, but lurking underneath is a monster of an engine. The Casa Performance SSR engine fitted has been tweaked even further, not only boasting an extra bit of capacity but considerably more power. It has been raised to 270cc and, along with a few other additions, is now producing 72bhp. So what has been done to improve the performance? The answer is a list of carefully integrated upgrades.

• Latest SSR LC air-cooled cylinder tuned for torque and power.
• Casa cases and cooler.
• Casa 5-speed cyclone close-ratio gearbox.
• 7-plate clutch and drive line.
• 48 mm Lectron power-jet injection carburettor.
• Custom down-draft inlet manifold and large Boyesen KTM reeds.
• Casa Mikuni fuel pump system.
• Modified Casa SSR exhaust system.
• Ultra Light AF flywheel with RPM triggers for shift lights.
• Kheper mapped 12-volt ignition.

All of this was developed over a couple of years by Gary Beard at Shiney Red Tuning, and the results speak for themselves. Firstly, it must be taken into account what the engine originally delivered, which, according to Casa performance, was a peak of 47bhp. On David’s engine, this has been raised to 72bhp, representing a 53% increase over the original spec, which was already impressive. But it’s the power spread that is the real star here. The spread of usable power is the most important figure, certainly if you’re racing. Though this is a road-going machine, if you’re going for out-and-out performance, it might as well be in race trim.

From the supplied graph, we can see that power starts climbing rapidly at around 5,000rpm and peaks at almost 10,000rpm. Even more staggering is that after 7,000rpm, the engine never drops below 40bhp. While the 72bhp peak at just under 10,000 rpm gets your attention, holding power above 40bhp throughout that later rev range is equally impressive. That means if you keep the engine boiling and within the 7k-10k power spread through each gear, you are going to accelerate seriously fast. However, just before you think, I would like to hop on and have a go, some implications regarding handling need to be ironed out.

Stretching the limit

Cast your mind back to the late 1990s and tuners managing 30bhp out of road-going Lambretta engines. It might sound a bit tame now, but back then, it was regarded as cutting-edge technology. This was uncharted territory, and a newfound problem began to emerge: front-end handling. Not so much the brakes, but keeping the front end down. Designers at Innocenti got the balance of the Lambretta just right, that is, until owners started shoving extremely powerful engines into them. This was prevalent for sprinters, trust me, I had plenty of issues dealing with it. There were two ways to solve the balance problem: either shove the engine back in the frame or move the front forward. Shoving the engine back requires some frame modifications, but it is possible if done on a full-frame Lambretta. It’s counterproductive, though, because it pushes the wheelbase further back, creating traction problems.

The other option is to stretch the frame in the middle, moving the front end forward to balance out the wheelie effect. This allows the rider’s weight to still sit over the rear wheel and cure the traction issue. Fabrication on a sprint frame is straightforward, but on a road-going Lambretta, it’s much more challenging. This is the method David chose; while the frame tube was the easy part, the leg shields would need cosmetic treatment. They had to be lengthened across the floor area, including the runners, not forgetting the brake cable, which needed to be extended since it is now positioned further forward.

There was a final part: the seat position, which required adjustment because the handlebars are much further forward, so unless you have long arms, you won’t be able to reach the controls. This was achieved by moving the seat slightly forward and sloping it so you naturally lean towards the front. That is the problem when you start to alter the frame geometry; everything else is now out of sync, and it’s a knock-on effect as you change everything to get it all back in line. David is a determined character and comes from a racing background, so he understands the challenges of developing an engine and chassis.

Never-ending

At first glance, when you look at this scooter, you think, ‘that’s a nice SX150 in standard trim’. Then you realise that something is different, almost as if the images have been stretched; of course, it’s not that, it’s the Lambretta itself that has. Then you look at the engine and see it’s a Casa Performance engine, but soon realise it’s a heavily developed one.

David isn’t the first to take a Lambretta kit or engine and push what was already deemed ‘the limit’, but, dare I say, he is possibly the first to take the SSR265 and improve it by this much. Development takes a considerable amount of time; 2 to 3 years have passed on this engine, and you realise there might be even more. That’s the thing about any two-stroke engine: there are so many different ways to extract more power from them. That is why I wasn’t surprised when David told me that more upgrades are coming, which can only mean more power. It becomes a never-ending cycle, and why not? Perhaps next year we might return to this project and see 80bhp from it. A far cry from the Li150 he owned in 1968, it might be, but he has proved that if you are determined enough, the Lambretta is a machine that can be continually pushed beyond the accepted boundaries.

Words: Stuart Owen
Images: David Krayem

Man & Machine

Name: David Krayem
Model: 1969 SX150.
Engine: Modified Casa SSR265 full-race engine.
Speedo: SIP electronic speedometer and rev counter.
Extras: Heads-up HUD sequential 6,000 – 10,000 shift light.
Gizmos: Digital air-intake, exhaust temperature gauges, and GPS speedometer.
Tank: 13 litre moulded fuel tank with sight level gauge.
Suspension: Adjustable gas SIP front and Protech rear dampers.
Handling: Custom adjustable steering damper.
Brakes: Casa front hydraulic disc brake with anti-dive.
Tyres: Dunlop high-spec road race tyres on Casa alloy wheels.