andy23 wrote:

I come to start my petrol strimmer today and it starts but it struggles
to tick over.



Sounds like the spark plug is covered in soot and needs cleaning. Just
use a wire brush or bit of emery paper to clean it off between the spark
gap. To get heavily sooted in the first place maybe you put too much oil
in the two stroke mixture?
Another thing that can happen is the spark plug ceramic cracking - that
happened to mine (different make) and gave me the same symptoms.