Honda CBR250R Tech 2011 Review

Shown with ABS (with sensor ring inside front rotor carrier), the black version is said to look more like the CBR1000RR to new riders aspiring to their first real motorcycle.

If not as vital for low rpm as it is for high, maximizing flow nevertheless aids engine power. This, plus the bore/stroke and big valves make us wonder what a performance tuner could do to open up this little powerplant for more high-rpm power.

Although Honda already has blueprints and tooling to churn out competent single-cylinder powerplants, as is characteristic of the engineering company, it penned a clean-sheet 249.4cc design just for the CBR250R.
Its engine alone has nine patents among 27 total – either granted or pending – for the new motorcycle. Fresh thinking was employed throughout the 359-lb machine (368 lbs with ABS) to make it as contemporary as possible.
Significantly at this price point is inclusion of Honda’s PGM-FI – a catch-all term that in this case denotes a 38mm Keihin throttle body working with computer-controlled ignition with digital transistorized electronic advance.
Honda says it has taken pains to straighten the flow path from intake to exhaust, but this DOHC is tuned for low-to mid-rpm grunt – more so than the parallel-Twin Ninja 250R. This notwithstanding, the 4-valve-per-cylinder’s bore, stroke, and valve sizes, nearly mirror the much-higher-revving CBR1000RR’s.

An all-new counterbalanced mill was made just for this world-production motorcycle.

An over-square 76mm x 55mm ratio is similar to its $9400-more pricey big brother’s 76mm x 55.1mm. Likewise the 250R’s intake valves are 30mm, compared to the 1000RR’s 30.5mm intake valves. Exhaust valves are an identical 24mm. Both intake and exhaust valves utilize unimposing-to-flow 4.5mm stems.

But here’s where the engine’s family resemblance tapers off. The 250’s compression ratio is 10.7:1, while the supersport’s is 12.3:1. The little CBR also lacks the big CBR’s dual 12-hole injectors per cylinder and computer-controlled digital transistorized ignition with three-dimensional mapping, let alone similar cam lift, duration and other high-performance tricks.
No, while the 250R may copy the fire-exhaling 1000RR in some respects, it is designed for low emissions, low maintenance, quietness, and efficiency. To further enhance low and midrange power, Honda says the intake and exhaust system were analyzed and tested to optimize ideal port/pipe length.
Peak horsepower arrives at a sedate 8500 rpm, and a linear torque curve climaxes at 7000 rpm, well below its 10,500 rpm redline. 
Compare this to the Ninja 250R’s 13,000-rpm parallel-Twin. At the tire on a dyno, it peaks with 25.4 hp at 10,250 rpm, and 13.2 ft-lb torque at 9500 rpm.

American Honda makes no power claims for the CBR250R, but our Indian correspondent was told that at the crankshaft it makes 25.8 hp, and 16.8 ft-lbs torque, with variances possible from market to market.

At the wheel, frictional losses will mean about 10-12% less, and when we dyno it, if this proves true, the Ninja will be the more powerful but more peaky. Both bikes allow for substantial over-rev, but Honda’s thumper delivers linear power lower in the rev range.
To handle the abuse Honda’s little engine might still receive from all those first-time buyers, and third-world riders, other innovations include a “spiny sleeve design” for the cylinder sleeve. Small “spines” added to the cylinder sleeve’s outer surface are intended to reduce operating temperatures, and thus distortion to the cylinder’s inner shape. This in turn is said to reduce oil consumption and blow-by gases.
To reduce emissions, an O2 sensor combines with the built-in air injection (AI) system, along with a catalyzer inside the exhaust to scrub the outgoing gasses.