On Fri, 23 Feb 2018 22:50:01 -0500, Meanie wrote:

On 2/23/2018 12:43 PM, 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?

I know it's always going to be the five things:
1. Gas
2. Air
---
3. Spark
---
4. Compression
5. Timing

Where compression and timing aren't likely to be changing on the fly, and
where spark "can" but also isn't likely to be uneven (given a reasonably
new and non-fouled plug) so that leaves gas and air.

I pulled the air filter in both engines, both of which I haven't used in
months, and they were both clean. I inspected the choke mechanism in both
engines (both of which have a fixed throttle below that) and it was clean,
even though I leave my gasoline in the tank full time all the time.

In the lawnmower, I just burned off the months' old gas (yes, I know most
of you do the "stabilizer" or drain over the winter task) and in the
sprayer, I dumped the years'old gas into a jar to use for cleaning label
glue off of bottles.

I assume the stoiciometric ratio is the problem, probably due to varnish,
I'm guessing, in the carb - but why the wheezing?

To be clear, I'm not asking about an engine that won't run, nor an engine
that isn't running at the right speed, but I'm asking about an engine whose
RPM goes from slow to normal to slow to normal to slow to normal in a never
ending no-load cycle.

Under load, the engines both work fine.

I should note this is a California set of engines, so there are no set
screws for the idle speed.

To summarize simply, it can't be a clogged orifice (I don't think) because
that wouldn't make the engines wheeze fast and slow and fast and slow
(would it? if so, how?).

If you need it, I can snap an audio or video but I hope that my
characterization of an idle speed that goes in and out is enough for you to
provide helpful advice (and not just advice to throw the gas away as even
if that is the cause - there has to be a physical reason for that to be the
cause).

I'm asking about the physical reason for the idle speed varying cyclically.


It's the diaphragm. Replace it.
Except most small engine carbs don't use diaphragms.

An engine that surges even with the carb totally clean on ethanol gas
with generally run perfectly on clear gas. The ethanol leans out the
mixture.

This is totally disregarding the FACT that ethanol gas, because it
absorbs moisture, tends to corrode copper containing (can you say
BRASS" ) parts - the "greenies".