POWERTRAIN :
Except for the Pulsar150 and the CBZ, all these bikes have different engine and transmission configurations with unique ignition mappings and head architecture. For starters the YBX125 has the least displacement of the lot at 123.7cc. Breathing is via two valves and the unit develops 10.9bhp and 10.4Nm of torque. An engine counter-balancer shaft is used to iron out rogue vibrations. Transmission of power is via a four-speed box which is the slickest of the lot. In terms of refinement, the YBX loses out at the top end of the rev-range, with vibrations rising to uncomfortable levels.

The Kinetic GF125 can rightfully claim to be the technological leader here,boasting a four-valve head to handle breathing duties of the 125cc single but it loses all this with its conventional carb when the industry is moving to CV instruments. A digital CDI ignition system is used, mapped to adjust timing relative to engine rpm for optimum Fuel Efficiency. The unit develops a commendable 12bhp though it develops just 9.81Nm of torque and that too at a high-ish 8000rpm. The unit develops most of its power at the upper reaches of the rev range and it is at this level that vibrations from the unit become physically intolerable while the decibels rise to deafening levels. Good for the first month of riding but after time this lack of refinement can become very painful. Starting is via an electric starter that is part of the standard spec sheet while transmission of power is via a five-speed box that disappoints in terms of actuation and shift quality. In fact it has been getting progressively worse and I have to employ the techniques learnt in years of riding a Bullet to effect clean gear shifts.

The CBZ derives power from a conventional 2-valve single displacing 156.88cc. No surprise that her power output at 12.62bhp and torque rating at 12.3Nm is the highest of the lot. Refinement of the engine isn't its strong point with harsh vibes becoming prominent very early in the rev-range. Transmission of power is via a five-speed box that doesn't pose any headaches except when finding neutral. An electric starter isn't offered even as an option.

Till recently the TVS Fiero boasted of the most technologically advanced powerplant in the motorcycle business and this unit yet impresses with its refinement and silky smooth power delivery. Displacing 150cc, the unit develops 12bhp and 10.5Nm of torque. A digital ignition system times the spark to perfection while a constant velocity carburettor ensures consistently precise metering of air-fuel mixture. Transmission of power is via a slick four-speed gearbox, though the engine really cries out for a fifth cog in the 'box.

The Pulsar 150 firmly establishes Bajaj engineers among the forefront of engine gurus in the country, earlier the sole hunting ground of the TVS boffins. The 143.9cc unit on the Pulsar boasts excellent detailing in the design of the combustion chamber, intake manifold length and airbox volume. A CV carburettor precisely meters the air-fuel mixture and ensures crisp throttle responses while a balancer shaft on the crankshaft works beautifully to eliminate harsh vibes. The head architecture is conventional with two valves instead of a high-tech 4-valve head that would make more power at the top end at the expense of refinement and usable low-end torque. The ignition has been optimised without need for a digital configuration. Starting is via an optional electric starter. To make kickstarting a breeze, a decompressor is built onto the camshaft. The unit develops 11.82bhp while max torque is rated at 10.82Nm. Transmission of power is via a five-speed box that is good with nice positive actuation though not in the same league as the Fiero or the YBX. Once in a while it does find a false neutral between fourth and fifth gears though these occurrences are very rare.

Performance :
Show without go is meaningless. When we talk about Performance, subjective evaluations get thrown out the window and objective evaluations backed solidly by printouts from our Datron data acquisition gear come into the picture. A day of back-to-back testing of these bikes on the test track threw up some commendable and some surprising Performances. On the track the YBX125 performed commendably and actually managed keep up with the larger engined bikes though it was a foregone conclusion that the YBX would cross the finish line dead last. The YBX took 7.8 seconds to touch 60kmph and 15.3 seconds to hit 80kmph from a standing start. These figures do not shame the YBX, considering that the CBZ (which has a 1.72bhp and 33cc advantage) takes 0.1 second more to get to 60kmph though it is over a second and a half quicker to 80kmph. The YBX clocked a max speed of 102.8kmph.

Next in line was the GF125, and expectations were running high what with its first-for-India four-valve head, digital ignition and a screamer motor. Initial acceleration of the GF is mighty hot, taking 3.9 seconds to get to 40kmph and 7.5 seconds to get to 60kmph, quicker than the larger engined Fiero and CBZ. However after 60kmph she rapidly loses ground eventually hitting 80kmph in 14.8 seconds. The GF peaks at a disappointing 96.4kmph at which point the vibrations are so harsh that they could kill you if you wear a pacemaker.

The Fiero took 7.6 seconds to get to 60kmph and 14.0 seconds to get to 80kmph.These figures are neck and neck with the CBZ that takes a slightly longer 7.9 seconds to get to 60kmph after which she pulls away from the Fiero taking 13.7 seconds to get to 80kmph, 0.3 second faster that the Fiero. The CBZ has a higher top speed than the Fiero, 108.8kmph versus 103.8kmph for the Fiero. The reason why the CBZ beats the Fiero at the top is because of the extra cog in the 'box. However the Fiero's trump card is the refinement of the motor that is superior to the CBZ's and doesn't feel trashy when pulled right up to the redline.

The Performance of the Pulsar 150 is simply amazing, pulling away right from the start line to post a time of 6.3 seconds for the 60kmph sprint and 12.1 seconds for the 80kmph sprint. This is a whole 2.4 seconds quicker than the next best CBZ, this in spite of a 12.8cc and 0.8bhp disadvantage. Top speed registered was a whopping 109.1kmph. If you notice the Pulsar figures are better than what she delivered when we road tested her last month, thanks to being completely run-in and then tested on the track.