SledgeHammer: CP’s 333cc touring engine for Lambretta | FIRST ROAD TEST

What is it?

The SledgeHammer is Casa Performance’s first proper go at a touring engine; as most humans understand the phrase ‘touring’. The CP boys might disagree. 

Their SST 265 was supposedly their ‘touring’ engine before, but I’ll be honest, not many people would prioritise 100+mph performance over fuel economy in a touring scooter. If a Lambretta can lap a circuit faster than the vast majority of Italy’s most brutal smallframe racing Vespas, then it’s not really touring: it’s a racing engine capable of feats of endurance.

They can afford the Sledgehammer to be different. If you want a fast Lambretta to show off with, then CP have a wealth of options available, right up to their insane 250 twin. If however, you want a dedicated tourer which is powerful but super easy to ride and will get you to rallies at speed without stress – or requiring in-flight refuelling before the end of the street – then this is really worth a look.

What’s the specification?

These are the main components of a partially-assembled engine kit:

• Casing: Casa Performance (CP) CasaCase modified for crankcase reedvalve induction 
• Cylinder: 79mm bore Nicasil-lined, air-cooled barrel and head. Single exhaust port, 6 transfer ports
• Crankshaft: 68mm stroke dedicated crankshaft with oversized crankwebs and 125mm con-rod
• Mag Housing: built into vertically-divided engine casing, using CNC flywheel cover
• Inlet: 4-petal reedvalve with dedicated reed housing and cast inlet manifold

Size comparison of the Casa SS225 kit (left) with the Sledgehammer 333 (right). The bore may be bigger, but so is the fin area. The Sledgehammer barrel has 8-point head fixing and 4-point exhaust fixing.

What was the concept?

Micky and Lorenzo started this project with a blank sheet of paper and a different perspective. Cooling first! 

When I first saw the Sledgehammer I was surprised that they chose to use long exposed studs, like a normal Lambretta barrel, to fasten the head, rather than short studs and a thick flange like their 265s.

There’s a point to this. It’s all intended to maximise the amount of available cooling fin area. Without a thick flange at the base of the barrel, and with no reedblock in the top of the cylinder blocking airflow, the barrel can be fully-finned all the way around, with extra-long fins on the hotter exhaust side. More surface area versus less aluminium to act as a heat sink. These prototype barrels are sand cast from 3D printed moulds with quite thick fins, but these will be slimmer in production. Even so, the massive 333.3cc engine ran with a cylinder head temperature of 135-185 Celsius, no matter what conditions I subjected it to.

Rather than trying to max-out the peak power, the cylinder has been designed with longevity in mind. The ports are relatively modest in width, allowing the piston and rings to get maximum support. Instead of radical port timings and high revs, it is the big-bore engine capacity that does the heavy lifting.

Test-fest: the black magic of 2-stroke expansion chambers. They are tested in straight-line format first as it’s easier than building ones to fit the scooter.

Does it vibrate?

Certainly not enough to qualify as an entertainment device for lonely nuns. Sorry Sister; it’s a Sledgehammer not a fanny hammer. The 68mm stroke dedicated crankshaft is well balanced to the 79mm piston, so it vibrates less than my TS1. 

It takes some coiling to fit such a long exhaust under a Lambretta engine…

You may need to drain the snake before you empty the fuel tank!

Is it economical to run?

Fuel use is not bad for the performance on offer. We first tested the 5-speed configuration in the mountains. Riding alongside a BGM RT195; which was also running a 30mm PHBH carb. Petrol consumption was about on par, depending on who was riding and how hard. The thing with the Sledgehammer is that you don’t have to work it hard to keep up with a slower scooter. It will do so on a fraction of throttle with zero burbling.

Having said that; the biggest effect on fuel economy was running it with a 5-speed gearbox. I also tried the engine with a standard 4-speed LI150 gearbox and while it pulled fine, it was definitely more fun and less thirsty with a Cyclone 5 Pro gearbox fitted.

The biggest improvement in running costs however, comes from using crankcase reedvalve and reducing the required percentage of 2-stroke oil. Crankcase reedvalve induction means that all the oil and fuel mix must pass the crankshaft; improving lubrication. With relatively low operating rpm and low cylinder temperatures the Casa boys confidently run the Sledgehammer on 2% fully synthetic Bardahl 2-stroke oil. For touring, that means a lot less cost than running a cylinder reedvalve motor at 3% or 4%, and a lot less oil to carry.

Yes, it rides fine with slower scooters. It can even be used to physically push them to go faster up big hills!

Can it ‘play nicely’ with other scooters?

This is the point that some scooter tuners often miss. It’s not difficult nowadays to get over 30hp out of a tuned Lambretta engine, but many of those who achieve it do so with compromises. Tuned motors are often spluttery at low revs when out of the power, so you have to constantly work the gearbox and throttle to ride in a slower group. Tuned air-cooled motors need to keep the fan spinning and fuel going in to stay cool. If you ride a tuned 2-stroke like a Driving Miss Daisy, then you can overheat and kill it. That’s not necessarily the fault of the engine; more a case of using the wrong tool the wrong way for the wrong job.

The worst thing about tuning Lambretta or Vespa engines to over 30hp is that you are simply stressing too many components beyond their limit. Narrow crankshafts twist at the crankpin, weak engine casings flex, insufficient gasket surfaces leak and suck air, weakening the fuel mixture; all to catastrophic ends.

The Sledgehammer is different because everything had been designed from the outset to cope. This is not a modified 10hp engine making triple the power. This is a dedicated variant of the CasaCase engine, which produces over 50hp in SSR265 form, reworked to make much less power, but still decent torque. For things like the main bearings, being fitted into a low-revving Sledgehammer is like a holiday.

How does it ride?

Unlike heavily-tuned engines, the Sledgehammer is not at all intimidating or difficult to ride. It pulls from ridiculously low revs in any gear, without a splutter. You can be lazy with your gearshift and just wind on the throttle to overtake. Riding it for hours is so much less tiring than something that vibrates like a jack-hammer or feels highly strung.

Any 30+hp scooter on 10-inch wheels is pretty quick in reality. I saw 140km/h (87mph) on the speedo of Micky’s LI series 1; which is about as aerodynamic as Dr Who’s Tardis. The Sledgehammer doesn’t force you to ride quickly if you don’t want to. Even relatively humble cars have a top speed of over 100mph, but that doesn’t mean you have to hit a ton on every visit to the supermarket. It’s more about having the power in reserve if you need it.

The best thing about this engine was the sensation that I didn’t need to worry about it. I soon forgot about the SIP speedo’s temperature gauge and learned to ignore the rev counter. With a big Oiltek fuel tank I didn’t need to panic about autonomy, unlike driving an electric clown car. I could just ride and enjoy the scenery or concentrate on my cornering lines.

I felt free to enjoy riding for riding’s sake. That’s refreshingly liberating.

This graph compares the power output of the Sledgehammer (red) with a BGM225 and box pipe (green) just to illustrate the performance in terms that people are familiar with. The Sledgehammer not only makes much more power, it does it lower down the rev range too. It may be quick, but it’s also really easy and unintimidating to ride.

Compromises

These are surprisingly few, but they will affect some people.

My wife Tracy had no trouble riding the Sledgehammer but starting it was a different issue. The Sledgehammer prototype does have a decompression hole (like the Quattrini M210 kit for instance) in order to make kick-starting easier, but it still takes a confident swing to fire it up. CP are aware of the issue and are likely to raise the hole even further to make starting easier on the production barrels.

The other issue is the carb layout. The motor fits largely without the need to modify the bodywork; particularly on S1 or S2 models. However, for Slimstyle Lambrettas you might need to cut a hole in the sidepanel for the carb to breathe through. 

Would I want to cut a carb hole in an original SX200 or GP200 sidepanel? Not so sure about that. 

My suspicion is that there will be future solutions that avoid the need for a hole, but at the moment with the supplied cast inlet manifold and a Dellorto PHBH 30mm carb, then you don’t have a choice.

Micky showing very few signs of guilt about cutting a hole in his LI Series 1 sidepanel

How do I get one?

To begin with Casa Performance have enough crankshafts to build a batch of 12 motors. Two of these are already sold to the first UK customers who took the prototype around the block with a straight-line development exhaust hanging out the back like a Bazooka.

The rest of the engine batch will be supplied on a partially-assembled basis. They supply the engine casing pre-fitted with engine mounts, crankshaft, inlet, reedvalve, cowlings and cylinder. To that, you add your choice of transmission parts, side casing, carb and ignition system.

Casa Performance expects that package to sell for around €3,800 Euros (£3304), but you’ll need to add the cost of a specific exhaust (which they are still finalising the design of) and either modify a fuel tank for carburettor clearance, or buy the dedicated Oiltek one.

Further down the line they plan to offer fully-built complete engine packages, ready to fit.

From my point of view, the part-built solution is great because many riders of tuned Lambrettas will already have a good quality ignition system, a suitable gearbox and a high-end clutch that they can fit themselves. Maybe with the aid of – ahem – a good workshop manual like edition 3 of the Complete Spanner’s Manual for Lambretta Scooters.

Verdict

Casa Performance have built some fantastic and crazy engines in the past. I’ve enjoyed riding them all but I’ve never wanted one in my scooter because they don’t do what I need from a rally scooter.

The Sledgehammer is different because it is enough of an all-rounder to ride 2-up, economical enough to act as a daily driver and confident enough to tackle motorways or traverse mountain passes. It’ll ride fast or it’ll ride slowly.

In short, this is an engine for regular Lambretta riders, as opposed to the pub talkers, keyboard warriors and dyno-dick-length comparers. 

Like its capacity, I think the Sledgehammer is going to be big.

Words, images and video: Sticky