This a motor that I didn’t know existed until late last year – and is a great use of an engine designed for other purposes. Motoring Weekly recently wrote about Coventry Climax racing engines and they repurposed water pump engines that went into cars!
Late last year I was looking at Karting New South Wales with a view to joining their board. Sadly I didn’t get on it, however in my research into the organisation, I was lead down an interesting path: one of the 26 clubs in the association was Subaru Karting NSW who (naturally) run four stroke Subaru engines. Another one was the 4 Stroke Karting Association of NSW. It was the first time I had seen a major manufacturer involved in grass roots karting.
Subaru’s industrial division produces a range of very small displacement engines for use with pumps, generators and other equipment. These are typically four stroke, overhead cam engines and so like Coventry Climax, Subaru have repurposed one of the smaller motors and renamed it from EX21 to KX21 – presumably the “K” means Karting!
The motor is an air cooled 211cc single cylinder with an upgraded combustion chamber to change the compression ratio from 8.5:1 to 10:1 for higher output. Other changes over the standard motor include better air intake flow and ignition timing. Power is improved by 30% over the original motor to 9.2hp. Fundamentally, the only common component between the EX21 and KX21 motors is the cylinder block – it appears that everything else has been changed, either to be bigger or to allow a smoother flow of air or exhaust. Every change improves the overall performance of the engine for racing purposes.
This is a great way to embed your name into future car owners – karting has drivers that start as early as possible!