Bloody hell , Hoony, where do I start ??
OK ,
J. A Prestwich was a proprietry engine manufacturer from southern UK, the company made everything from small two stroke lawnmower engines up to the thundering 1100cc V twins.
From the 1950s the 350cc Grasstrack engines , the 500cc Grasstrack and Speedway engines and the KTOR, or more commonly known as the 880, 1000cc V twins were the best known.
The Long Five , long conrod ,five stud 500cc was the most common in the 50s followed by the Short Four, short rod, four stud 500cc, it in turn was followed by the 4B engine in the very late 60s, it is the most common engine in Aussie Dirt track in the 70s, it had a longer overlap, higher lift camwheel and a more modern carby plus a better ign. system
In the early 70s, JAP brought out the 84S, a new engine with a shorter stroke 90mm by 84mm bore, as against the 4B's 99mm stroke by 80mm bore, hence the name, 84S, it was followed by the 84C , a four valve, dohc jobbie.
One of the tricks was to fit an 84S piston to a 4B, making it 540cc or there abouts, the bloody things would pull your arms off !!
The last JAP engine to win a World Speedway was a 4B fitted to a ESO frame ridden by Ove Fundin in the 60s and the last Longtrack title by a JAP was an 84S ridden by Egon Muller in the early 70s.
Bro Jim rode an 84S in a BSA frame in classic road racing, used to hose Manxes off, they weren't happy !!
Foss
