Posted: 05/10/2015 at 09:13
Thank you David, that is most helpful, at least now, I know where to start looking!
You're welcome, Meomye.
I've just reread your original message and would confirm that the 'mixture' you refer to is the amount of petrol/air being delivered to the carburettor......the symptoms you refer to would indicate that this 'mixture' is too rich.
There will be two adjusting screws on the carburettor, one being for adjusting the petrol 'mixture', the other for adjusting the engine's tick-over.....*these screws can be identified by a small spring beneath the screw head.
*The purpose of these springs is to prevent movement caused by vibration.
Finally, I would say that although this is only a five minute job for a mechanic, if you don't feel comfortable with it, take it to a lawnmower service shop....or bring it to me.