Stage6 R/T FL 70cc cylinder crankcase C-One / RC-One / 2Fast

Stage6 R/T FL 70cc Cylinder for racing crankcases with Flanged Mount (FL) fitting such as Malossi C-One, RC-One, 2Fast Passion or TPR Factory. The new generation of one of the most iconic Stage6 R/T cylinders, completely redesigned after years of development on the dyno and track.

Here we are no longer simply talking about fitting a 70cc kit so that the scooter goes faster. The R/T FL70 is designed to build a complete Racing engine around it: 70cc, 47.6 mm bore, original 39.3 mm stroke and 90 mm connecting rod, with an architecture designed directly for FL crankcases.

With the right setup, Stage6 states approximately 29 hp at 14,500 rpm. And what is interesting is not only the peak figure: during its development, the aim was to achieve a broad, usable powerband, avoiding an engine that only works well within an extremely narrow RPM window.

This is especially noticeable on the track. A broader powerband makes the engine less critical with regard to variator and transmission tuning: if the RPM drops slightly when exiting a corner or temperature changes affect behaviour during a long session, the engine has more margin to remain within its effective range.

The difference of an FL cylinder

The Flanged Mount system makes it possible to work with crankcases specifically designed for high-performance Racing cylinders. Instead of trying to push a conventional crankcase beyond its limits, the assembly is designed from the outset to provide the cylinder with the space and feed it needs.

That is why this R/T cannot be fitted to an original crankcase. It requires a compatible FL-type crankcase, such as C-One, RC-One, 2Fast Passion or TPR Factory.

The cylinder uses 5 transfers and an exhaust port with a central bridge. This configuration makes it possible to have a large exhaust area while keeping the piston ring under control as it passes over a large port, something especially relevant in an engine designed to operate at such high revs.

The body is made of aluminium with Nikasil coating, a common combination in Racing engines thanks to its ability to dissipate heat and provide a durable working surface for the piston.

A cylinder head adjusted cylinder by cylinder

Stage6 does not simply fit the same insert to every unit. Each cylinder is measured taking machining tolerances into account and, depending on the result, the corresponding insert is selected from three available heights: 2.3 / 2.5 / 2.7 mm.

It is a detail that makes quite clear the level for which this kit has been designed: ensuring that the final geometry of the assembly remains within the intended values instead of assuming that all machined cylinders are exactly the same.

The cylinder head is modular, with a separate insert and orange anodised cover.

Exhaust designed as part of the cylinder

The exhaust outlet uses a 5-axis CNC-machined manifold fixed to the cylinder by means of four bolts.

Its function is not only to allow the exhaust to be fitted. It is designed to provide a progressive transition from the cylinder's oval outlet to the exhaust inlet, avoiding an abrupt change in section right in an area that is critical to the operation of a 2-Stroke.

Sealing is achieved by means of three O-rings: one on the cylinder side and two on the exhaust connection. This helps prevent the typical leaks of unburnt mixture and oil around the exhaust outlet that appear on many Racing engines.

What is needed to reach those 29 hp?

The figure stated by Stage6 corresponds to a complete and correctly tuned setup. For reference, the manufacturer developed the cylinder working with:

• Stage6 R/T FL70 Exhaust.
• Stage6 R/T inner rotor Ignition.
• Stage6 R/T Oversize transmission.
• PWK 28 mm Carburettor.
• Stage6 by V-Force Reed valve.
• Long gearing.

In an engine at this level, everything has to work together. It makes no sense to fit a cylinder capable of operating above 14,000 rpm and then limit it with a small intake, an incorrect exhaust or a transmission unable to keep it within its powerband.

One of the advantages of the FL70 is that it does not force you to begin with extreme preparation of the crankcase transfers. It is designed to be fitted, jetted and tuned on a compatible FL crankcase. Even so, Stage6 has left enough material so that tuners who want to go further can work the cylinder and develop even more specific setups.

Technical characteristics

• Manufacturer: Stage6 R/T.
• Model: FL70.
• Displacement: 70cc.
• Bore: 47.6 mm.
• Stroke: 39.3 mm / original.
• Connecting rod length: 90 mm.
• Gudgeon pin: 12 mm.
• Material: aluminium.
• Coating: Nikasil.
• Transfers: 5.
• Exhaust: port with central bridge.
• Piston: 47.6 mm.
• Ring: 0.8 mm.
• Cylinder Head: modular, insert + cover.
• Available insert heights: 2.3 / 2.5 / 2.7 mm, selected by Stage6 according to cylinder tolerances.
• Head cover: orange anodised.
• Exhaust manifold: 5-axis CNC-machined.
• Exhaust fastening: 4 bolts.
• Exhaust sealing: 3 O-rings.
• Spark plug thread: long M14.
• Reference power: approx. 29 hp at 14,500 rpm with the proper setup.
• Fitting: FL-type crankcase.
• Use: competition only.

Includes

• Stage6 R/T FL 70cc Cylinder.
• Piston and corresponding components.
• Modular Cylinder Head.
• CNC exhaust manifold.
• Gaskets required for fitting.
• Fitting hardware.

Important: this cylinder is NOT compatible with original or conventional crankcases. It must be used exclusively with a crankcase prepared for the FL - Flanged Mount system.