What mostly makes a small engine "wheeze" fast & slow, fast & slow, fast & slow?

[Ralph Mowery]

That is about what I do. I try to put the Stabil in the 2 5 gallon gas tanks I usually fill up at a time with the ethanol free gas before I leave the house. That should really mix it up as the gas goes in the cans. I have 3 of the 5 gallon cans so when 2 of the get empty I fill them up. Summer time is not too bad as I use about 2 or 3 gallons per week. However I may go from November to March or so and not use any. I do like to have atleast 10 or more gallons round for the small generator incase the power goes out in the winter. It seldom does, but one never knows.

Sofar all the small engines start up on the 'old gas'. Best starting engine I have is the tiller. I usually just run it once or twice in the spring or late winter to get a small garden ready. Then I let it run all the way out of gas. For the last 10 years it will start on one or at the most 2 pulls of the starting rope. That is with a fresh fill up of the 4 month old gas.

[slate_leeper]

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-

[Clare Snyder]

You get lean hunt and rich roll. With rich roll the muffler turns black. With lean hunt pulling on a bit of choke makes it better. Rich roll gets worse. Generally the "period" of lean hunt is longer than the "period" of rich roll - or put another way the lean cadence is slower.

[krw]

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. ;-)

[Clare Snyder]

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 - - -