Wondered if anyone could diagnose an engine problem... It's a Hayter Spirit mower - 4 stroke petrol engine, pretty basic.
When I use it, it will run fine for ~5 mins, then for no apparent reason it will idle really roughly and at ~10% revs. After ~2 mins of really rich smoke puffing out it will just kick back to life and full revs again.
When I looked at the spark plug it's really black. I have changed this but it just ended up oily again. I have changed the oil but still no improvement. The oil level isn't too high.
Here is an exciting video of it when it is in 'rough running mode'. For some reason in the vid at the end I tipped it up which seemed to improve things but normally if you just let it run rough for 2 mins it starts up again.
Any thoughts? Maybe it needs a new Johnson rod? I looked under the black plastic cover to see if there was any sort of "Run well" switch that might have flicked to 'Off', but there wasn't.