ProTip: Yes check the air filter first

engine running very rich with lots of black smoke?

engine running very rough like a paint mixer jiggling around?

spark plug, boot, wire, igniter, coil, whatever, all is fine?

carb is clean inside and out, and adjusted, choke plate open and so on?

all linkage = good?


But it "Runs Like a Deere" (or in my case, like a Kawasaki ... ) with the air cleaner cover off. But put it on and gently press it down and cover the two bolt holes and the world starts to fall apart.


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In all my years I've never seen an engine so horribly brought to its knees by what seems is an air filter "only a little dirty." And this one had the foam around it also.

Absolutely, good post, the air filter is one of the most neglected & inexpensive parts of an engine. Engines need to breathe.

Something else to check is pull the dipstick and see if the oil smells like gas. The gas fumes in the crankcase will get pulled into the engine when the air filter it installed. I have seem water, oil, gas in air filters that shut them up permanently.

What is the engine model?

txmowman said:

What is the engine model?

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In my case it's a FC420v in a LX176 mower, but it could be any similar thing I suppose. My 265's use a very similar (but slightly larger) air filter/cleaner for their FC540v engine. At any rate I'm not sure it's relevant since so many mowers have setups that look like this.

Those older, external vent carbs are not as forgiving with dirty air filters like today's internal vent. Great engine though. Keep up that maintenance and it will survive many more years.

txmowman said:

Those older, external vent carbs are not as forgiving with dirty air filters like today's internal vent. Great engine though. Keep up that maintenance and it will survive many more years.

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That is good to know, thanks.

The only thing is, any filter manufacturer will tell you that you can't tell whether a filter needs replacement or not by looking at it. A filter that is covered with grass clippings may have plenty of life left and one that looks new can actually be clogged. I'll list two examples of this below.

Notice I didn't say anything about cleaning. The manufacturers of paper pleated filters will tell you not to do this because after the filter is installed, it's sealing surfaces conform to the sealing surfaces of the air cleaner housing and 'take a set' and there is a good chance the filter will not seal properly when re-installed.

The best way to determine filter condition is with a restriction gauge.

FWIW, the two filter technical field reps I've spoken with told me that far more engines are ruined by well-meaning people 'cleaning' their filters.

Example 1: Kenworth truck with pneumatic trailer hauling dry bulk chemicals. These trucks have a PTO-driven Roots blower which is used to load and unload the trailer. In this case, we loaded out of hopper railroad cars and unloaded into storage silos at soap plants. This process generated LOTS of dust. When the truck was facing into the wind, not problem. When the truck was facing away from the wind, so much dust settled on the truck that we carried a small broom to clear the windshield well enough to drive. The engine and Roots blower inhaled so much of that dust that you could barely even see the filter elements in the air cleaner cans. Yet the restriction indicators said the filters were still good.

Example 2: Cub Cadet with pleated paper air filter with oiled foam wrapper. Engine manufacturer says to clean the foam wrapper every 50 hours and replace the element at 200 with the caveat "more often under dusty conditions." Cub Cadet says to clean the foam wrapper every 10 hours and replace it at 100 hours, with the same caveat. The pleated paper element ALWAYS looks brand new at 100 hours, yet is past due when used in mowing, which certainly is "dusty" conditions.