Spark plug almost as important. A wire brush will clean that and as a
VERY
VERY rough guide, the gap between the electrodes should be the thickness
of
a thumb nail.

I realised those - they were dirty but cleaning them was the first thing I
did when I started working on the mower I did toothbrush and meths
treatment on the plug - scraped away much of the carbon on it.


Great :-))

Though the clean and dry air filter sponge soaked up much more oil than I
expected... should I squeeze out as much oil as possible (to allow the
airflow) or is it better to keep some in (to collect bits of dust, I
assume)?

If it is the sponge type without the cardboard stifeners/case etc, then I
would wash it out in hot soapy water. It needs to be clean to allow the air
to go through, leave a film of oil in it and it will clog again.


I don't think it was originally very oily, but the previous owners
of the mower did zero maintenance on it so that's probably not a guide.
FWIW in testing (on concrete, not cutting anything, not dusty air) I ran
it
with no air filter until I got it started.

You can run the engine without the air filter and that should prove one way
or the other. If it runs OK without the filter but not with it, there is
your problem ........ 'sort of' because you are now down to tuning.

BUT, to run it on concrete without the filter is not a good idea. The filter
is there to stop impurities entering the engine and scoring the bores of the
cylinder. Concrete is very abrasive and any dust thrown up and into the
engine will not do it any good. If you have a large sheet of ply or
harboard, run it on that

Mike


--
The Royal Naval Electrical Branch Association.
'THE' Association if you served in the Electrical Branch of the Royal Navy
Reunion Bournemouth August/September 2007
www.rneba.org.uk
"Navy Days" Portsmouth 25th - 27th July 2008. RN Shipmates will have a Stand