NO: 202
DATE: 06/03/20

The new sprayer with the small engine started and ran flawlessly in the beginning, but now it is harder to start and doesn’t run as smooth.

The problem may be too many short run cycles where the engine does not have a chance to get up to its optimal running temperature.

This sparkplug shown has a carbon build up.

Fouled spark plug has excessive carbon deposits due to improper spark plug heat setting.

Spark plugs come in a range of heat settings from 2 to 11, ranging from a low of 932° to a high of 1472° Fahrenheit, with the lower numbered plugs generating more heat than the higher numbers. Running a small engine in short bursts, perhaps averaging less than 10 minutes per run time, does not permit the engine to build up enough heat to burn off hydrocarbons and impurities in the oil.

Remove the spark plug and check for carbon deposits, black soot on the electrode. It could mean that the combustion process is not getting enough air due to a dirty air cleaner. If the air cleaner is clean, carbon buildup is likely the result of the engine not running long enough to get hot enough (842° F) to burn up the left-over combustion by-products.

This spark plug is from a correctly operating engine.

Honda engines come with a spark plug with a heat rating of 6, a middle of the road rated plug. If you have carbon buildup, you may want to try a hotter plug with a heat rating of 5. If you are still having issues, you may want to go down to 4.

Your small engine’s operating temperature will depend on engine speed and load. In the case of a spray pump, load is the pump’s operating pressure. The higher the pressure, the greater the load. If your sprayer runs at low rpm and pressure most of the time, it may rarely reach 842°. Try a hotter (lower numbered) spark plug and see if it makes a difference.

Side Note: I did mention “burning impurities in the oil.” A naturally aspirated engine is always going to burn a certain amount of oil. The harder the engine works, the higher the operating temperature, the more oil it will burn. Don’t forget to check the oil.

Any questions please refer to user manuals or call (866) 609-4172 x102 for the Operations Manager.