An inline-four engine arranges all four cylinders in a single row along a common crankshaft. This configuration requires only one cylinder head, one exhaust manifold, and one valvetrain, which reduces mechanical complexity and production cost relative to a V arrangement. In a racing context the primary advantage of the inline-four is its straightforward serviceability and the predictability of its power delivery.
The conventional inline-four fires at even intervals of 90 degrees of crankshaft rotation. This even firing order produces smooth, consistent torque delivery to the rear wheel. In MotoGP, Yamaha and Suzuki have been the most prominent users of the inline-four configuration. Yamaha has run inline-four engines in MotoGP since the class was established in 2002.
A significant variation on the standard inline-four was introduced by Yamaha's 2009 YZR-M1, which used a crossplane crankshaft that fires cylinders at uneven intervals of 90, 270, 180, and 90 degrees. This design prevents pistons from simultaneously reaching top dead centre and produces a firing order similar in character to a V4, giving the rear tyre more time to recover traction between power strokes. The Yamaha crossplane inline-four was credited with improving rear traction during corner exit.
A V4 engine places its four cylinders in two banks arranged in a V shape, sharing a common crankshaft. Compared with an inline-four the V4 is shorter along the longitudinal axis of the motorcycle, allowing a more compact overall package. The shorter crankshaft is also stiffer, reducing susceptibility to torsional vibration, though it introduces additional complexity through the requirement for two cylinder heads, two exhaust manifolds, and two valvetrains.
The most common V4 angle in MotoGP is 90 degrees. At this angle the engine achieves a perfect primary balance and produces uneven firing intervals — power strokes are not evenly spaced — which gives the rear tyre brief recovery periods between impulses. Proponents of the V4 argue that this characteristic improves traction on corner exit and makes the bike more controllable under acceleration.
From 2020 onward the majority of MotoGP manufacturers have used the V4 configuration. Honda has historically run the RC213V with a 90-degree V4 layout. Ducati's Desmosedici has used a V4 since the marque entered MotoGP in 2003. KTM's RC16 and Aprilia's RS-GP are also V4 machines. The convergence of multiple manufacturers on the V4 layout reflects accumulated evidence that its packaging and traction characteristics suit the demands of modern MotoGP machinery.
The inline-four is narrower from the rider's perspective and simpler to engineer and maintain. Its conventional even-fire variant delivers smooth, progressive power, and its layout creates a narrow frontal profile that can aid aerodynamic efficiency. The crossplane variant narrows the gap in traction character relative to a V4.
The V4 is more compact lengthwise, which can allow chassis designers more freedom in weight distribution and swingarm geometry. Its inherent uneven firing order produces a torque character that many riders have found easier to manage at the limit. The configuration also allows the engine to be mounted lower in the chassis due to its reduced height, potentially lowering the centre of gravity.
Neither layout is intrinsically superior. The competitive history of MotoGP shows that both configurations have produced world champions, with outcomes depending as much on overall chassis development, electronics, tyres, and rider talent as on engine architecture alone. The debate between inline-four and V4 continues to inform engineering decisions as manufacturers develop machines under successive regulation cycles.