We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember The Natural Philosopher
saying something like:

Check the basics first - it might just be dirty blades.

Usually a blocked or partially blocked jet.

I had one like this. New jet every year, new photocell every other year
when wiping it failed to work.

It's the case that simple, basic checks and replacements can do wonders
- and it's surprising (or not) how many people never bother. I have all
the gear now but it's not necessary for keeping a burner running
reasonably clean. Otoh, it was surprising how much more efficiently a
burner could be made to run with the combustion analyser than just by
eye - a good 10% more.
--

Dave