With a Red Bull in hand, I am writing this high over the clouds. Most of all, I'd like to sleep, but I can't shake the hard-hitting Aprilia RXV 550 out of my mind. The RXV 4.5 and 5.5 launch was at Riserva Naturale Pino d'Aleppo in the middle of rural Sicily. I guess Aprilia made the landowner an offer he couldn't refuse, as he sacrificed his field to the roaring RXVs.
Luckily, I rode the RXV 450 first on enduro terrain. Both bikes come standard with Michelin Enduro Comp III tires. Believe me: You need every bit of grip you can get, especially on the RXV 550. We also rode the two RXVs on a grass track, where there aren't many bikes that will beat the 450. Who would have imagined a highly competitive off-road 450cc V-twin only a few years ago? V-twins are for touring and adventure enduros, not for off-road racing. But make no mistake-this is a race bike. The RXV 450 is a serious challenge for Honda's CRF450X and KTM's 450 EXC, particularly since the Italian puts its massive horsepower down better than the singles. But with the AMA banning twin-cylinder race bikes in pro racing, the bike's immediate future is somewhat cloudy.
RXV 450 is all about loads of usable power. The 77-degree V puts out around 55 bhp in a much smoother, more tractable way than a single. When I first started the engine, it was evident this off-road machine is very powerful (it sounds rowdy, too). Even with all the horsepower, that rear tire digs in and the bike surges forward. Power is spread over a very broad range, and there's plenty of overrev. You quickly develop biceps like Popeye's riding this bike. Compared to a single, you have much more power to play with anywhere in the powerband but with less engine-braking. That puts more importance on braking and riding style in corners. Seat height is a tall 39.2 inches to allow plenty of ground clearance and wheel travel. The V-twin engine allows for an even slimmer frame than a 450cc single. Balance is superb; it is something the twin engine lends itself to naturally. Despite the fact that Aprilia claims the engine tips the scale at no more than a single, the RXV weighs more than high-end singles. A claimed dry weight of less than 220 pounds is not unusual on singles; the RXV 4.5 claims 258 pounds. The actual weight of a KTM 450 is about 255 pounds ready-to-ride with an empty tank, so if Aprilia is accurately reporting the bike's weight, the twin isn't overly porky. Titanium valves and magnesium covers help to keep the weight of the engine down, but we suspect the complex chassis and exhaust system add weight compared with a single. However, the balanced package and power delivery compensate for the extra weight. Our riding did not involve any big challenges, so it is hard to tell how the extra weight would have affected us on tougher terrain.
The suspension was perfect for gravel roads with small stones-soft enough to absorb small hits but still firm enough for high speeds. The standard setup is ideal for light enduro riding, in other words. For jumps and hitting big rocks or crests at speed, the fork springs are a bit on the soft side. There is very little sag, but the rear shock squats under power. The rear suspension is a single shock sitting on a gorgeous aluminum swingarm. The shock also has high/low-speed compression settings. The front suspension is a 45mm USD adjustable fork. The SXV supermoto models got a differently calibrated 48mm USD fork and a wider swingarm to fit wider wheels. This makes it difficult to convert an RXV for supermoto. Gearing is different to suit the diverse riding styles. All of the XVs are very single-minded and made for racing. The adjustable fat handlebar and Domino grips are nice but are placed too far back for my liking. Too often I felt as if I was hanging by my arms rather than achieving full control. (This was particularly noticeable on the powerful RXV 550.) On the grass track, I could easily point the front where I wanted to go without using too much muscle and still be able to keep the throttle open. The RXV 450 grips better than most bikes out of bends-you can really go for it. The RXV 450 blew me away, and I was truly worried when it was time for the 550.
 "You quickly develop biceps...  "You quickly develop biceps like Popeye's riding this bike". | | |