The yzr M1 is the moto gp 800cc ballistic missile, the closest to it in road bike terms is the 2010 yamaha r1 which uses a similar design crossplane crankshaft, (often referred to as a big bang crank), if you watch footage of last years gp and see either lorenzo or rossi and listen to the engine you'll note it has a lazy sound compared to the screaming of the honda / suzuki's. These are all four strokes.
The lc was a range of two strokes lc referring to liquid cooled and the powervalve being a disc valve system which opened at a certain rev range giving a 'boost' of sorts, it was something all stroker msnufacturers played with to try and even out the performance as all two stroke machines are tuned via the length of exhaust and have a narrow 'optimum' power band, the expansion chamber, (spannies), in racing circles, goes part way to tuning this, the powervalve was an additional extension allowing exhaust gas out or restricting it to build back pressure. Sadly the eurocrats have killed two strokes and very few are available new, the poor learners today have to put up with heavily restricted wheezing four stroke singles.
The rd's were available in 125 single,250 twin, 400 & 500 variants, a whole generation grew up inhaling that luxurious blue smoke and they have a real cult following now.