A lawn mower, which has had no modifications to the engine. Governed engines, 3650 RPM max. (No load) Basically Normal mower with the deck removed Sometimes used in fun events or relay races, but not used in racing the below classes.
Racing Lawn Mower Classes and Engine Classification
Class 1 Mower
Flathead single-cylinder side valve engines up to and including 28 ci (458cc), and overhead single-cylinder engines less than 28 ci (< 458cc) originally manufactured for lawnmowers.
Class 2 Mower
Engines originally manufactured for lawnmowers, up to and including 32 ci (524cc)single or twin cylinder.
Class 3 Mower
Engines originally manufactured for lawnmowers, up to and over 32 ci single or twin cylinder. The engines should be engines used in residential and lifestyle type ride on mowers.
Non-Modified Class Mowers
Some small Modifications may be made in these engines as it is in our nature to tinker and try different ideas, these small changes are very difficult to police and the classes are based on an honesty system, some changes may give small gains but not substantial enough to warrant being put into the Modified classes.
Non-modified engines, must use the stock unmodified factory OEM parts listed below for their model engine:
- Intake manifold
- Crankshaft Camshaft.
Changes that are permitted are listed below:
- Removal of governor
- Removal of charging loom
- Spacers under valve springs
- Heavier valve springs
- Light plaining and porting of heads
- The use of heavier aftermarket conrods for reliability purposes
- Carburettors may be changed or substituted for different brands
- Carburettors must be mounted on the stock intake manifold
- Allow the use of after-market air filters
Modified Class Mowers
All three engine size categories
All Modifications allowed
If Cam is modified or an after-market camshaft is used then it is compulsory to use an approved alloy flywheel
No turbo, superchargers, or forced induction