Short Stroke/Over square Engine: As the name signifies the Stroke is shorter than the Bore. Due to the relatively shorter stroke, the engine revs fast and is more suitable where a quick build of power is important, more importantly where the bikes make power at higher rpms.

Some examples:

• RTR 180 (62.5mm X 57.8 mm) Bore x Stroke
• Pulsar 220 (67mm X 62.4 mm), 180(63.5mm X 56.4mm) Bore x Stroke

Long Stroke/ Under square Engine: As the name suggests the Stroke is longer than the Bore. Due to the longer stroke, the engine makes good torque at relatively low rpms. It is important where the bikes’ pulling more (torque) at relatively low rpms is more important than the top speed.

Some examples:

• Royal Enfield Classic 500 (84mm X 90mm), Classic 350 (70mm X 90 mm)
• Hero Honda Karizma (65.5mm X 68.2mm)

The one exception to the above rule is the pocket rocket Yamaha R15 (57mm X 58.7mm) which is strange as R15 is a track oriented bike.

Square Engine: As a square has both the sides equal, here also the Bore and Stroke are of almost same size. The engine tries to strike a balance between torque and top speed

Some Examples:

• Yamaha FZ-16 (58mm X 57.9mm)
• Honda Unicorn (57.3mm X 57.8mm)

All these engines have their own advantages and disadvantages and it depends on the rider to decide what kind of motorcycle he/she needs.