For many Lambretta riders, the goal isn’t simply building the fastest engine possible — it’s creating a scooter that delivers strong torque, smooth power delivery, and dependable performance over long distances.
That’s exactly what the BGM PRO RT cylinder kits were designed to do.
Available in 195cc and 225cc versions, the RT kits have become one of the most respected touring upgrades for Lambretta engines. They offer modern performance while maintaining the reliability and rideability that classic scooters demand.
The Story Behind the RT Cylinder
The RT (Race-Tour) cylinder concept was originally developed by Mark Broadhurst of MB Developments.
Broadhurst had already built a reputation for producing highly tuned Lambretta engines, but many of his early cylinder conversions required extensive hand finishing and specialist tuning, making them difficult and expensive for the average rider to replicate.
The goal behind the RT project was to change that.
Working in collaboration with Scooter Center Köln, the idea was to produce a modern touring cylinder kit that could deliver strong performance straight out of the box, without requiring complicated modifications or expensive custom machining.
Development began around 2012, with the first mass-produced BGM RT kits launching in 2013. The aim was simple: create a bolt-on performance cylinder that delivered the torque and rideability of a well-tuned stage 4 engine while remaining reliable enough for everyday riding and long-distance touring.
Built for Torque and Rideability
One of the key differences between the RT kits and many race cylinders is the focus on usable power rather than peak horsepower.
Instead of chasing extreme revs, the RT cylinders are designed to deliver:
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Strong low-end torque
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Smooth mid-range power
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Comfortable cruising speeds
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Reliable long-distance performance
This makes them ideal for:
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Touring scooters
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Rally riding
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Two-up riding
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Long motorway journeys
For many Lambretta riders, this type of power delivery is far more useful than a highly strung race engine.
RT195 – The Perfect Fast Road Cylinder
The RT195 was designed for Lambretta 125–175 based engines and uses a 65mm bore to produce 195cc.
It provides a noticeable performance increase over standard engines while maintaining excellent reliability. When paired with the right carburettor and exhaust setup, a typical RT195 engine produces around 18–22 horsepower, with a broad torque curve that makes the scooter easy and enjoyable to ride.
Because of its flexible power delivery, the RT195 works particularly well with:
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25–30mm carburettors
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Clubman style exhausts
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Touring expansion pipes
For riders building a fast road Lambretta, the RT195 is often considered one of the most balanced options available.
RT225 – Big Torque Touring Power
For Lambretta 200 engines, the RT225 increases capacity using a 70mm bore.
The larger displacement produces significantly more torque, allowing the engine to pull taller gearing and maintain comfortable cruising speeds even on long journeys.
A well set up RT225 engine can typically produce 22–25 horsepower, while still maintaining the smooth and predictable power delivery the RT kits are known for.
This makes the RT225 a popular choice for:
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Long-distance touring builds
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Two-up riding
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Rally scooters
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Riders who want effortless motorway cruising
Modern Engineering for Classic Engines
The BGM RT kits combine traditional Lambretta design with modern engineering.
Key features include:
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Aluminium cylinder construction
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Nicasil plated bore for improved durability
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CNC-machined components
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Specially designed piston assemblies
The cylinder head is CNC-machined with an anti-warp design, helping maintain correct tolerances under high temperatures and extended use.
Early versions of the RT kits experienced some piston issues, but these were later resolved with upgraded Italian-made Meteor pistons, which significantly improved durability and reliability.
A Proven Touring Cylinder
Over the past decade the RT kits have become a common sight on Lambretta engines across Europe.
They are frequently used on scooters travelling thousands of miles to rallies and events, where reliability is just as important as performance.
By bridging the gap between standard engines and full race builds, the RT cylinders provide a modern solution for riders who want stronger performance without sacrificing reliability.
Recommended Setup for a BGM RT Engine
As with any performance Lambretta engine, the final performance and reliability of the RT195 and RT225 kits depends heavily on correct setup.
While the RT kits are designed to be relatively straightforward to install, taking the time to set up the engine properly will ensure you get the best possible results.
Running-In Period
A proper running-in period is essential when installing a new cylinder kit.
Recommended running-in distances are:
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RT195: approximately 200 miles
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RT225: approximately 400 miles
During this period the scooter should be ridden with varied throttle input, avoiding prolonged high speeds or heavy load. Stop-start riding around town is ideal as it allows all components to bed in gradually while giving you the opportunity to monitor carburation, ignition timing and general engine behaviour.
Squish Clearance
Correct squish clearance is important for both performance and engine reliability.
For RT kits the recommended base squish measurement is around 1.3mm, although a range between 1.2mm and 1.6mm is generally acceptable during assembly.
Once the engine has been heat cycled and gaskets have settled, the ideal running squish figure is typically around 1.2mm, with anything between 1.1mm and 1.5mm considered safe.
Ignition Timing
Ignition timing will vary depending on the exhaust system used.
Typical starting points are:
For expansion exhaust systems (e.g. JL3):
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Static timing: 17°
For box or clubman-style exhausts:
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Static timing: 16–17°
Variable ignition systems may use slightly higher idle timing figures before retarding at higher RPM.
Carburettor Setup
The RT kits work well with a range of carburettors depending on the overall engine build.
Common options include:
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Dellorto PHBL 25mm
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Dellorto PHBH 30mm
Typical running-in jetting setups include:
PHBL 25mm (airbox):
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Pilot jet: 48
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Needle: D22 (3rd clip)
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Atomiser: AQ262
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Main jet: 92
PHBL 25mm (open mouth):
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Pilot jet: 50
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Needle: D22 (2nd clip)
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Atomiser: AQ266
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Main jet: 100
PHBH 30mm (open mouth):
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Pilot jet: 58
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Needle: X2 (2nd clip)
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Atomiser: AV264
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Main jet: 115
After the running-in period, carburation should always be checked and fine-tuned if necessary. Many riders choose to have this done on a rolling road.
Fuel and Oil
Fuel quality plays an important role in performance and reliability.
While normal unleaded petrol can be used for short journeys, super unleaded fuel is strongly recommended, particularly for longer journeys or when using expansion exhaust systems.
A 3% oil mixture is typically advised. This equates to:
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30ml of oil per litre of petrol
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150ml per 5 litres
High-quality fully synthetic two-stroke oil is recommended for maximum engine longevity.
Gearing Recommendations
The RT kits work well with a range of gearing options depending on riding style and engine setup.
BGM generally recommend a final drive ratio between 4.80 and 4.94.
One of the most popular setups is:
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Italian LI150 gearbox
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16/46 sprockets
Another commonly used option is the SIL GP200 gearbox, often paired with 19/47 or 18/46 sprockets depending on exhaust choice and riding style.
Supporting Components
To ensure reliable fuel supply and engine operation, a few additional upgrades are recommended.
A fast-flow fuel tap should deliver approximately 550–600ml of fuel per minute at operating height.
Many builders also recommend:
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High-quality air filters such as RamAir or Breath Sweet
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A five-plate clutch for improved durability
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85W/90 gear oil for the gearbox
Finally, pressure testing the engine after assembly is highly recommended. Air leaks can cause incorrect jetting, poor running and potential engine damage, so ensuring the engine is properly sealed is an important step in any build.
Final Thoughts
The BGM PRO RT195 and RT225 cylinder kits represent one of the most successful Lambretta performance developments of the modern era.
Developed through collaboration between experienced tuners and specialist manufacturers, they combine modern engineering, strong torque and long-distance reliability in a way that perfectly suits the way classic Lambrettas are ridden today.
For riders looking to upgrade their engine for fast road use, touring or rally riding, the RT cylinder kits remain one of the most trusted and widely used options available in the Lambretta world.