2021 Honda CRF450R and RX

Honda’s CRF450R was among the vanguard of the four-stroke motocross revolution at its launch back in 2002 and 19 years on a ground-up redesign takes the CRF into its seventh generation.

The 2021 bike’s improvements start with a 2kg weight loss courtesy of a new frame, swingarm and subframe, which are also claimed to improve the bike’s ‘rigidity balance’. The alloy chassis has narrowed main rails, mirrored in the slimmer swingarm, and alone saves 700g compared to the old model. The subframe cuts another 320g off the bike’s mass. While no more flexible in terms of twist, the revamp makes the frame 20% less rigid in lateral flex – a move claimed to improve corner speed, steering and traction. It’s geometry has also changed, with a steeper rake and less trail (27.1°/114mm, down from 27.4°/116mm), and 8mm more ground clearance at 336mm. Dry, the whole bike comes it at a mere 105.8kg.

Both the 49mm Showa forks and the matching rear shock have been revalved, while the rear spring uses lighter steel to cut 200g from its weight.

A shorter, lighter and 10mm lower seat is used, attached with fewer bolts to make maintenance easier, while the whole biker’s body is a full 7cm narrower than the old version.

As you’d expect from a full-on competition bike, there are exotic materials to be found including a titanium fuel tank – redesigned for the 2021 model – and big-name brand components including Renthal bars and DID aluminium rims.

Engine-wise, the bike gets fractionally more power (up by 0.8bhp) thanks to a significantly larger air box and redesigned, 46mm throttle body. A repositioned fuel injector improves efficiency and throttle response while the decompression system is also redesigned.

New oval exhaust ports – an idea shared with the CBR1000RR-R Fireblade – further improve efficiency, and feed into a single downpipe and end can, replacing the 2-1-2 system of the old model and saving more weight. A hydraulic clutch replaces the old cable-operated one for a lighter lever feel and more consistent behaviour.

The cross-country CRF450RX has been given most of the same changes as its motocross sibling, including the frame, subframe and suspension updates – albeit with different damping and spring rates – as well as the same bodywork, engine and exhaust revisions.

Overall, it enjoys even greater weight savings, losing 2.3kg for a dry weight of 107.6kg.

Yamaha’s 2021 YZ250F and 450F

Honda’s unveiling is the latest in a string of 2021 off-road bike unveilings, following Yamaha, Kawasaki and KTM.

Yamaha’s 2021 motocross range includes an updated YZ250F with a redesigned version of its unusual reverse-head four-stroke single. New exhaust cam profiles, an improved intake system and updated muffler give a wider power band, while the transmission tweaks give smoother shifts.

The YZ250F also gets an updated frame with ‘fine-tuned’ rigidity levels, combined with revised suspension front and rear and a new braking system.

Yamaha’s larger YZ450F, which was given a complete revamp for 2020, gets little more than revised graphics for 2021.

Kawasaki has also concentrated on its 250 for 2021, with changes to the KX250 including a 1.4hp power increase thanks to a 350rpm higher rev ceiling, and the welcome addition of an electric starter and hydraulic clutch. The engine changes also include revised cams, new valve springs, a tweaked combustion chamber, longer con rods and changes to the crankshaft.

The KX250’s frame is also revised, with the usual mantra of ‘a better overall rigidity balance’ as its target. Much of the chassis is shared with the larger KX450. Suspension changes include revised shock linkages and new settings, while the brakes are also revised with a KX450 front master cylinder and a new rear disc.

Like Yamaha’ Kawasaki has left its 450-class machine largely untouched for 2021. The KX450 gets little more than minor revisions to the clutch construction and a new piston skirt coating to reduce friction, while a 28.6mm Renthal Farbar is now standard. The 2021 KX models are on sale in late August at £7799 for the 450 and £7499 for the 250.

Kawasaki’s 2021 KX250 and 450

KTM was the first of the big players to unveil its 2021 off-road models, back in June, with tweaks across the SX range of motocross machines.

The 450SX-F gets changes to its piston and crankshaft, new rocker arms and revised engine cases. Along with the 350SX-F and 250SX-F, it can also access the ‘myKTM’ app via an optional connectivity kit, allowing on-the-fly adjustments and the ability to save preferences.

The firm’s 2-stroke range changes include a new piston and clutch for the 125SX and 150SX models.