16-02-19, 03:10 PM
If you suspect valves aren’t closing I’d start by measuring clearances.
BP, Shell etc have pricier versions of petrol loaded with additives that supposedly clean the valves. However, the Fazer’s carbs are set to run rich, presumably to allow a safety margin in case of low octane fuel. This does mean that there is always a fair amount of soot in the exhaust but nothing to worry about.