I have a petrol lawnmower (Mountfield Empress) that was working perfectly until I cracked the shell.
I have dismantled it but have been unable to repair. You might be more successful.
I would like to give you the parts, if you think you might make some use of them, rather than scrap the machine.
Note that the accompanying stock photo is of an assembled machine.
Dismantled petrol lawnmower (Ballintine BT27)
This offer has been gifted to someone and is no longer available.