Ride on mower running horrible!

My CastelGarden ride on has started running rough.

It starts fine but then starts missing (I think) that is what is happening.

I have a utube video here, as is best for anyone to hear what it is doing:
http://youtu.be/m4g3brLQNmE

I have a utube video which gives the sound it is making, far better than me describing it!
http://youtu.be/m4g3brLQNmE

The engine is;
Engine.jpg

Any hints would be much appreiated.

PJ

Attached Images

• Engine.jpg (348.2 KB)