The Street Twin carries forward the tubular steel cradle frame design from the Bonneville, but now this chassis has received ample changes in terms of its geometry. The largest mechanical change, however, is the engine. It might look like it’s the same from the earlier bike, but now this parallel- twin motor houses an increased capacity to 900cc and also sports liquid cooling. The block still retains the cooling fins just like an air-cooled motor, making itmore efficient, and allowing the boffins at Triumph to keep the size of the radiator almost the same as the oil cooler from the outgoing Bonnie. This new motor now revs lower than the older 865cc unit and makes lesser peak power (55hp vs 69hp), but is tuned for higher power delivery in the usable rpm range, i.e. between 2,750 and 4,750rpm, and in this zone, the Street Twin makes 22 percent more power. More importantly however, this new engine makes more torque – 80Nm, and all of it is delivered from as low as 3,230rpm. In the process of making the new engine more usable in real-world conditions, another change has been the cylinder firing order which has gone from 360 degrees on the outgoing bike to 270 degrees on the Street Twin. This really goes a long way in improving low-end torque delivery and also gives a bike a distinctive sound (which is also enhanced thanks to the new exhausts). This engine’s highlight is its refinement, and this vibe-free temperament ensures that the bike is well-liked by a wide variety of riders.
The new motor’s torquey nature is immediately apparent whether riding through congested city roads, open highways or twisty hill roads. The bike’s high tractability makes it a joy to ride in these slow-to-medium speed conditions, and should keep most riders happy as long as they don’t feel the need for some high-revving action. Acceleration is brisk, but not neck-snapping in any way, and the Street Twin can go from zero to 100kph in 6.14 seconds.
The Street Twin only gets a five-speed gearbox, but the ratios are very well spaced and it makes good use of the wide torque spread. The shifts are a bit on the clunkier side, and the action between first and second gear seems rather vague, but once rolling, you can keep the bike in high gears, even in traffic. In urban conditions, another massive benefit is the new slip-assist clutch, which keeps the clutch lever action smooth and light. The Street Twin now also gets high-tech throttle-by-wire which makes for smooth throttle inputs. As part of the updated electronics package, the bike now gets a traction control system. Now this system is quite rudimentary in nature and quite intrusive at times, but when the surface gets loose, you’ll be glad to have this safety net.