Maintaining engine filters

Routine maintenance is something that nitro RC'ers either love or hate to do, but luckily for the maintenance-haters of the world, only a few steps are required to perform what is arguably the single most important task for maintaining a healthy nitro engine: cleaning and property oiling your vehicle's air-filter element. This vital step is critical to long life, consistent performance and trouble-free tuning for your engine.

Engines are like lungs; they require a constant supply of clean, fresh air to operate property. You wouldn't run a marathon wearing a dust mask clogged with dirt and actually expect to perform well, would you? Operating a 2-stroke engine with a dirty filter is no different from that, and if you really neglect your engine's filter, you run the risk of overheating the engine and destroying it entirely. I've seen plenty of racers and bashers run their nitro vehicles with grungy air filters, so this month's column explains how easy it is to clean and re-oil your nitro burners air-filter elements

Manufacturers usually supply their kits with dense, white-foam air filters, but some still use the paper element/foam prefilter assembly. Regardless of the construction, packaged air filters in RTR and unassembled nitro kits are rarely oiled for you by the manufacturer. If you're unsure whether your kit's foam element is pre-oiled, simply squeeze the unused filter between your fingers. If your fingers are sticky or have oily residue on them, the element has already been oiled, so whether the element is white, gray, or black foam, give it a quick squeeze before you crank up your engine, and oil it if necessary.

OILING CLEAN FILTERS

Oiling foam elements requires only enough filter oil to get the job done; where filter oil is concerned, more is not better! If you use too much oil, you can easily clog the foam element, and your engine will suffocate from a lack of air. To oil an element without making a mess, toss a clean filter into a zip-lock bag and drizzle in a few drops of filter oil. Close the bag, and work the oil into the element by squeezing the bag, and then remove it. It's that simple! Filter oil is sticky, so tiny dust partic[es get trapped in the filter before they can be passed through to the engine.

Occasionally, a foam filter will react badly to a specific brand of oil and may become so swollen that it's no longer usable. In such a case, simply start over with a brand-new filter. To be safe, use only the filter oils recommended by the vehicle, engine, or filter manufacturer.

CLEANING DIRTY FILTERS

Cleaning dirty fitter ele- ments is far more economical than simply throwing them away or waiting to see how long your engine will run with a filthy filter. There are several ways to clean the various types of filters; check out these recommendations to see which method is best for your vehicle's filter.

* Paper-element filters. These are cheap to maintain and replace, but there's an easy way to make a paper element last indefinitely: maintain a clean, well-oiled prefilter. These little foam outer filters are wrapped snugly over the paper element and protect it by prefiltering the dust and dirt particles before they contact the paper element. If you've allowed the paper element to become soiled, replace it; otherwise, clean the prefilter by performing the same maintenance routine as we recommend for cleaning foam filters.

Never wash or oil a paper filter element because water will break down the paper, and oil usually clogs the filter and restricts airflow excessively. To restore a paper filter, blow compressed air from the inside of the filter; this will help to dislodge at least some of the dirt the filter has trapped.

Foam-element filters. These dense, foam-rubber elements do an excellent job of filtering dust and dirt, but air can't flow into the carb if the element's outer surface is clogged. Begin by pulling the entire filter assembly off the engine's carb and removing the filter element. The filter assembly usually has gunk around the assembly base (where it's attached to the carb neck) and its filter area, so clean the entire assembly under warm running water with a squirt of grease-cutting dish soap. Scrub the assembly thoroughly, and dry it with paper towels or a clean shop rag. Set it aside, and allow it to dry completely before you reassemble it. Filter assemblies should be cleaned before you reinstall the element.

With the proper products, foam elements are a snap to clean. Warm water and dish soap are one option, but you'll have to scrub repeatedly for best results. Soap the filter generously, then work your fingers and thumbs into the foam while you hold it under warm running water. Wash the element until it looks like new, and allow it to dry overnight before you re-oil it. For a more effective and thorough cleaning, pick up a K&N "Filter Recharge" kit at an automotive-- parts store. This kit, which costs about $15, includes a pump bottle of filter cleaner and an aerosol can of filter oil. Wet the dirty element with warm running water and then