Fitted with a supercharger and intercooler, the ULTRA 260X's liquid-cooled 1,498 cm3, In-line 4-cylinder engine produces an output much greater than a normally aspirated engine of the same displacement. The roots type supercharger ensures powerful and instant acceleration even from a standing start. A number of modifications to the engine increase output to 260 PS, once again making this the most powerful production PWC in the world.

 The roots type supercharger is known as a fixed displacementsupercharger. This design produces large amounts of boost even at lowrpm, for instant and powerful acceleration right off of idle. Withevery revolution it force-feeds the engine 2 litres of air, ensuring astable supply of high-pressure intake air at all rpm. The result is avery flat and meaty torque curve and step-free power across the revrange, with none of the time lag associated with turbochargers. Theoretical volume is 2,060 cm3/rev, and the maximum boost pressure is0.8 kg/cm2 [11.4 psi]. This arrangement delivers idealised intakepressure the instant the throttle is opened, for phenomenalacceleration.

To ensure ideal intake air pressure, not one, buttwo air bypass valves are used. A vacuum air bypass valve is used tobalance air pressure upstream and downstream of the throttle body. Itworks mostly at low and medium rpm. A second, regulatory air bypassvalve aids the vacuum air bypass valve in preventing over-boosting whenthe throttle is shut (or opened) suddenly. Should the system'sspecified maximum pressure be exceeded, the regulatory air bypass valveis activated, allowing air to escape.

Efficiently cooling thehigh-pressure intake air is a liquid-cooled intercooler. Frictionbetween the air molecules heats the intake air to extremely high(power-robbing) temperatures, but the intercooler cools the air backdown to ambient temperature. Cooler air results in high engine output.

The engine's over-rev range extends to 8,900 rpm.

Inconelexhaust valves with superior heat resistance are fitted for highreliability. (Valve sizes are: 33.4 mm intake / 28.3 mm exhaust.)
Bore and stroke measure 83.0 x 69.2 mm.

Compression ratio was raised from 7.8:1 to 8.4:1 for increased engine output.

New,STX-15F-style high-lift cams contribute to the increased engineoutput. Intake lift increases from 7.8 mm to 8.5 mm; exhaust, from 7.5mm to 8.2 mm.

Ignition timing was advanced 4o, resulting in increased engine output.

New cast pistons feature revised crowns with machine finishing. The higher quality pistons have greater durability.

Acheck valve added to the coolant passage between the cylinder jacketand the water muffler ensures the cylinder walls are kept at the idealtemperature. When the engine is operating over 2,000 rpm, the ballvalve keeps the cooling water from leaving the cylinder jacket.

Head cover revised for improved appearance.

Lower crankcase strengthened around the oil-return passage to better cope with the ULTRA 260X's increased engine output.