Triumph Daytona 675R
While the entire motorcycle is new for 2013, the big news centers around the engine. It’s still 675cc, but now with reduced stroke (49.6mm from 52.3mm) and greater bore (76mm vs. 74mm) than before. The result is an engine that now revs to 14,400 rpm, 500 revs higher than before. (Its more oversquare architecture still isn’t as radical as the Daytona’s chief rival, the MV Agusta F3, which uses a 79.0mm bore and a 45.9mm stroke. –Ed.)To accommodate the larger bore yet keep the same overall physical size of the engine, it utilizes a sleeveless cylinder design with Nikasil-coated bores for reduced friction. The cylinder block is now separate from the crankcase.
Compression is up to 13.0:1 from 12.65:1. Each piston pin is nitride coated for strength, with the big end bearing growing to 35mm from 33mm. Likewise, the lower crankcase is redesigned to reduce power loss due to oil drag, and its main bearings are upgraded—all measures to help cope with the increased power.
Each cylinder is fed fuel via two fuel injectors, a first for Triumph. New titanium intake valves are the same 30.5mm diameter as before, but stem length is increased half a millimeter to 4.5mm. Its shape is also revised with more material to create a more dome-like appearance Triumph says improves flow.
Exhaust valves remain steel bits, but diameter is reduced from 25.5mm to 24.2mm, thereby reducing weight slightly. All told, the new valvetrain weighs 17% less than before. Camshafts are also new, with increased lift.
The transmission receives a slew of updates for smoother, more precise engagement, especially between the first two gears, a critique noted from Triumph’s race teams. A slip-assist clutch reduces lever effort by 25% compared to last year and keeps the rear wheel in check, enlisting the help of the ECU to open throttle butterflies if needed. Finally, the 15-tooth countershaft sprocket is down a tooth from last year for improved acceleration.
On the chassis side, the new frame and front subframe were designed to more efficiently feed air to the cylinders. The air intake scoop is 39% larger than last year, and the air’s path is more direct than before. But the biggest noticeable difference is the new stainless steel exhaust. Gone is the old under-tail unit, in is the sleeker, under-engine piece with side exit. All in the name of mass centralization.
What does all this add up to? Triumph says max power at the crank is increased 3 horses and torque up 1.5 ft.-lbs. to 126 hp and 55 ft.-lbs., respectively, compared to the old bike. More importantly, graph overlays provided by Triumph indicate the new mill has a stronger midrange and healthier top-end.
A new subframe provides a narrower profile but is also responsible for the 10mm decrease in seat height in the standard 675 (32.3 in. vs. 32.7 in.). The new swingarm retains its adjustable pivot point for racing but is slightly shorter for quicker handling.
