RS 250 replacement cylinder kit
The Aprilia RS 250 remains popular with two-stroke fans. From World Championship tracks to the road, it remains a timeless legend. To help keep the venerable racer pointing in the right direction, Italian performance specialist Athena has developed a next-generation cylinder kit for the RS 250 (and the Suzuki RGV 250).
Described as "unique on the market", Athena's Standard Bore Cylinder Kit is fully compatible with the original, requiring no modifications - "just 'next-gen' components for reliable and long-lasting performance."
The kit consists of a ready-to-install aluminum alloy cylinder with Motor-Niksil treatment, lightweight flat-top piston with anti-friction coating and high-conformity gaskets for consistent sealing across all surfaces.
The 56 mm, 250 cc (12.0:1 Compression Ratio) cylinder is made of a high-silicon-content aluminum alloy CNC machined for precision tolerances. No changes to the engine crankcase required, and the kit includes the oil tank mixer fitting and the brass bushing for the exhaust valve shaft, all preassembled. The shaft features a threaded valve seat instead of the classic pressed-fit type, making any future disassembly and reassembly operations much simpler.
The Athena technicians also redesigned the coolant hose as the original sleeve installed on the Aprilia-Suzuki cylinders can corrode. They created a separate brass sleeve that can be screwed directly into the cylinder - simplifying the maintenance of this essential component.
The seats of the head studs have also been redesigned and, unlike the original, they are no longer in contact with the water passages of the cylinder, guaranteeing optimal contact pressure and maximum sealing in all conditions.
The inside of the cylinder wall is coated with Motor-Niksil to ensure smoother sliding of the piston, less friction, and reduced wear of the piston rings, for durable and consistent performance. The Motor-Niksil treatment provides extra hardness and superior strength inside the cylinder, limits wear and helps maintain the nominal bore size over time.
In addition, the inner diameter of the CNC-machined exhaust crossbar eliminates the risk of the excessive expansion that could damage the piston. The Athena flat-head piston kit was designed and developed specifically for long-life and to maximize high-performance. "We selected a high-silicon-content aluminum alloy to ensure a low coefficient of thermal expansion. Consequently, the mating tolerances between piston and cylinder are much tighter.
"The piston skirt is lighter for maximum performance, and the surface has been coated with Molybdenum Disulfide to reduce friction, lessen noise, and improve sliding of the pistons.
"To ensure constant and effective lubrication of the needle roller cage bearing and the connecting rod small end shims (spacers), in all conditions, Athena technicians have designed a CNC machined window on the intake side of the piston skirt. On the exhaust side, the skirt features holes for the lubrication of the exhaust crossbar.
 |
| Two-piece Athena exhaust valves kit with advanced two stage design. |
"The included piston rings are made in Japan from a special steel and feature a chromium nitride coating applied using a PVD process, ensuring low friction, smoother sliding of the pistons, and a longer lifespan.
"The piston pin is biconical for greater strength and lightness and is made of a nitride-treated aeronautical steel alloy to guarantee maximum hardness and minimal friction."
Also seen here is a two-piece Athena Exhaust Valves Kit with two-stage design is made for greater reliability and enhanced performance.
ATHENA
