Overview
The MX2 category of the FIM Motocross World Championship – the premier level of motocross competition globally – is one of the most hotly-contested. We were tasked with creating an engine for Dixon Racing Kawasaki that would be capable of competing within this competitive and demanding environment.

The Challenge
There were two primary design considerations on this project, both linked to the specific demands of the championship.

Developing top end performance is not necessarily the best approach to motocross. A motocross engine requires a wide power band, so the torque curve shape is important, especially when a team includes riders with different styles.

Limited engine cooling is also a key element to consider in designing and creating an MX2 powertrain as the radiator can often become blocked by track material.

The Solution
The first step was to carry out a 3D scan of a OEM production engine before building a one-dimensional GT Power model from airbox to exhaust tip.

The engine was then run on one of our transient dynamometers in order to gather key engine data to correlate the model. This ensures the output of any changes in the model represent the real-world impact.

Kits of key components, including the pistons and camshafts, were manufactured in-house, assembled into the engines and supplied to the team.

Engine Specification

No. of cylinders: 1
Capacity: 250cc
Power: > 50bhp
Rev limit: 16.000rpm
CR: 16.0:1

Focus on: pistons
With decades of experience producing performance powertrains, we know what it takes to produce race winning engine components. Bringing that expertise to the MX2 engine, we designed a very short, lightweight piston to reduce friction caused by the side loads. To minimise crevice volume, the top ring is only 4.5mm below the piston crown; the crown itself is designed to best suit the combustion chamber shape in the head.

The piston is machined from solid in our piston manufacturing facility before being DLC coated. The crown is polished and coated for a number of reasons; it reduces carbon build-up; maintains better heat transfer; aids gas flow and flame propagation over the surface.

*MXGP2018 Image – Photographer Ray Archer