Have you checked the HT cap ?
I have had issues with failure of the suppresion resistor built in to the cap & this gives “odd” running. These are typically 5 K Ohm & can be measured by unscrewing the cap from the HT lead and checking the resistance bewteen the lead side & plug side of the cap – the ones I have had problems with have gone open circuit. HT caps are cheap enough to fit a new one if yours is old.
Another source of “odd” running can be accidentally fitting a resistor spark plug (if an NGK, a plug designation with an “R” in it) with a resistor plug cap fitted. Easily done if you fit an Iridium or Platinum plug, which only seem to come in resistor flavour – a non-resistor HT cap is required with these.
As the old saying has it – 99% of carburation problems are ignition related & vice versa.
Nigel B.