On Mon, 26 Feb 2018 11:22:20 -0800, Oren wrote:

On Sun, 25 Feb 2018 20:21:55 -0500, wrote:

On Sat, 24 Feb 2018 19:49:59 -0800, Oren wrote:

On Sat, 24 Feb 2018 10:40:37 -0500, slate_leeper
wrote:

On Fri, 23 Feb 2018 09:43:12 -0800, ultred ragnusen
wrote:

What mostly makes a small simple engine (such as the Honda GC 160 that runs
my pressure washer or the Honda engine that runs my lawnmower) "wheeze"
fast & slow, fast & slow, fast & slow while idling under no load?


Had that problem with my John Deere X300. After a lot of google
research, I found a possible cause as "clogged air filter." I removed
mine, washed out the foam prefilter and tapped out the paper filter.
Reinstalled, and everything ran fine. Started surging again about a
month later, so I replaced the paper filter. Been fine ever since.

-dan z-

Good point and correct. It leads back to fuel OR oxygen starvation. In
your case the dirty filter restricted the air mixture.

A bad spark plug did it on my lawn tractor. I guessed both the fuel
and air filters before settling on the plug. The next step was to
pack it up and take it to someone who knows something about engines.
;-)

Yep, a fouled plug can be a problem. Just need fuel, oxygen and spark
to get 'er runnin'.
But "generally" if it starts OK but rolls at idle, the plug is not
the problem. A plug will - and again I say "generally" either cause
difficult starting or cutting out under load -VERY seldom an idle
surge, or hunt.

If allowed to run too long with a "rich roll" the plug will
eventually foul.

If run too long too lean under load a plug will "glaze" - but MUCH
less likely on unleaded fuel than it was with leaded gas -
particularly high sulpher leaded, which produced a yellow-green lead
sulphide glaze - also known as Galena - one of the earliest used
semi-conductors.

Used to see a lot of "4 transistor" Toyotas back in the day - - -