It's a pretty 'ancient' thread, but since I've some knowledge on the topic, thought I'd chime in regardless...
YBR is a THUMPER! Just one cylinder, one piston, one spark plug, one everything to keep the costs down, obviously.
Yamaha's R6 on the other hand is a screaming inline-4! Means 4 cylinders, 4 pistons, 4 everything! It has basically 4 150cc engines stitched together to work as one!!! An R1 has basically 4 250cc engines!!! And because R6 has more pistons, it can scream upto an eye watering 14,000rpm because of lighter & relatively un-stressed crankshaft whereas our CG gets out of breath at just 9,000rpm! It's because 1 piston engines really put a ton of strain on the engine internals.
EXAMPLE:
A Suzuki DR650 makes 35HP because it's 1 Cylinder or SINGLE. A Suzuki SV650 makes 75HP because it's a 2 Cylinder or TWIN. A Triumph Speed Triple makes 100HP cause it's 3 Cylinder or TRIPLE. Kawasaki ZX-6R makes 130HP cause it's 4 Cylinder or inline-4. Some even comes with 6 cylinders! Like Honda CBX1000 ( <classy!) or BMW K1600 Series grand touring or GT Bikes...