Speedway Bike Explained:

The style for the bikes have changed over the years due to engineering and manufacturing changes. The engines up to about 1990 were all what is commonly know as 'upright'. This is mean exactly what is says. The engine is placed in an upright position in the frame. The post 1990 bikes have what is known as a 'Laydown' engine. This means that the engine has been physically laid down in the frame giving a lower centre of gravity. The power ratio has also increased with this change as well.

The original engines began with a 'total loss' oil system, which meant that the actual motorcycle frame was used as the oil tank and before every race, this was filled and the oil that wasn't burnt in the mechanical process, was pumped out onto the track surface. The later uprights and the newer style laydown engines, were designed to have a re circulating oil system that needed changing after each meeting. Currently, a professional rider will change this oil after 2-3 heats depending upon his set-up.

Many manufacturers have attempted to compete in the speedway engine world, but only two remain competitive. Jawa from the Czech Republic, and GM from Italy. Other names that will be heard from the past would be JAP, Weslake, Godden, ESO, Datzmann etc....