Following a discussion, the Track Racing Committee have amended SR 4.24
The amended rule can be found below and in the updated ACU Track Racing Standing Regulations – https://www.acu.org.uk/Uploaded/1/Documents/2022%20ACU%20Library/Track-Racing-Standing-Regulations-2022-MASTER-V3.pdf
4.24 POST-CLASSIC Post 1976 UPRIGHT SOLO GRASSTRACK MACHINES
These guidelines are for Solo machines in accordance with equipment that was in common use between 1976 and 1990.
a) Standing Regulations. All machines must comply with the Standing Regulations for Track Racing as given in the current edition of the ACU Handbook with the exception of the following:
b) Frame. The frame should ensure that the engine is mounted in a near upright or vertical position. The rear suspension, if fitted, should incorporate a swinging arm with suspension units mounted on each leg of the swinging arm and onto the rear sub frame. (MONOSHOCK REAR SUSPENSION IS NOT PERMITTED)
Both telescopic style and leading link type front forks are permitted.
c) Four Stroke Engines. The engine will be of a type commercially available post 1976. The engine will have two inlet and two exhaust valves per cylinder. The inlet port of the cylinder head may be angled towards the right hand or left hand side of the machine or mounted centrally from the cylinder head.
The engine the lubrication system may be either a recirculatory system or a total loss system. If the engine is a total loss system, then an oil catch tank must be fitted as per Grass Track Technical Rule 4.20.