Instead of featuring a main model and a significantly less efficient "B", here we find two models that are almost equivalent ― though there is a tiny bit more focus on the racing bike that we will be dealing with here, than on the Easy Rider-style cruiser.
However, it is nicely packed with features for a model of that size and a very limited dimensional constraints: fore and rear suspension, three-cylinder inline engine with transmission and a chain drive to the rear wheel, openable fuel tank, steerable nose and a retractable kickstand.
▪ IDEAS AND CONCEPTS
One can find a nice demonstration of the flexible axle connector usage, along with the clever positioning of the engine and many other components at an angle, which is generally quite difficult with Lego. The clever bodywork structure itself is a great idea, and if you are into building motorbikes, you will definitely get some great hints from the 8051. Among moving parts, there is no particularly new system involved.
For a medium-sized set, quite a nice amount of useful parts: two large wheels, two large and one heavy-duty small spring, several dozens of chain links, a large 40-tooth gear and a couple of smaller ones, three engine cylinders with its pistons and stuff, and some custom bodywork panels. There is also an amount of beams, though insufficient for large experiments. And ― tons of 3-stud-width axles!
None officially supported, though I suppose it should be relatively easy to modify the bodywork and the overall design, and perhaps modify it to look like some specific motorcycle. However, since the model is tightly packed with parts, there isn't too much freedom to change in its interior.
No specifically designed manual controls on this one; roll it on the floor, look at the engine running, steer and occasionally stop (and extend the kickstand).
▪ WEAK SPOTS
It is not the easiest to build and requires some patience with parts loose during the construction. Also, it would be quite difficult to build almost anything else substantial out of this set, than an another motorcycle. It would be nice to see the engine operation more clearly, but since it's so constrained by design, construction and form, it would probably make it look somehow awkward.
▪▪ VERDICT ▪▪A fine piece of mid-sized Technic, though perhaps a little bit more designer-oriented than usual models, with plenty of purely decorative parts. However it looks undeniably great, and without those parts, it would not resemble a motorcycle in the first place. Some cool technical parts to add to the collection, especially for the road-going projects, and some clever construction tricks to learn, though applicable primarly on ― other bikes. It is nicely operable and fun to play, but doesn't have a power feature that makes your neighbour's children start packing stuff for Legoland.