If your Kensington, Classic petrol or Liberty 43 mower is making a high level of noise from the side casing, especially after your mower cylinder has tried to cut a strong obstruction, then you could have damaged the nylon (plastic) drive gears which are coloured green (these are pink on older models).
These gears are designed to fail if obstructions are encountered by the cylinder to protect your machine from expensive damage. These gears are quite inexpensive. We have made improvements to these gears in the last few years and the latest design are green in colour.
You can find cheaper copies of this gear on the internet, but they have copied the old inferior pink gear and didn’t do that well. Beware of imitations.
We have created a video that helps explain how to change this gear and you can watch it here.