[XJWoody]

Often I hear of low-kickback chains being called “safety chain.” This is a misnomer, as there is very little inherent safety. It’s design is such that as the chain travels around the top & front of the bar tip (from 0° to 90° as viewed from the right side) there are “bumpers” (humps) in between the cutter teeth which restrict how deep the teeth can bite. This helps limit rotational effects known as kickback. Most standard chains lack these bumpers, and will take a “normal” bite as it travels around the top & front of the tip. Low-kickback bars tend to have a smaller nose radius, which decreases the size of the 0°-90° kickback zone by maximizing the effect of the bumpers. Within the Stihl family, their low-kickback chains and bars are color-coded green, and their others are coded yellow. Both styles can cause horrific injuries if allowed to contact flesh.

Saws and other two-stroke tools are pretty basic in terms of care and maintenance requirements. Well cared for, a good-quality saw should give many hours of reliable service. The basics include always using fresh high-octane fuel mixed with quality oil, at the proper ratio. This is typically 50:1 for modern-era equipment. With the addition of ethanol into pump gasoline, mixed two-stroke fuel has a useful life of three months or less. Stale gas will cause engine problems (and potential for catastrophic failure) if it is used, and one should never use gas with more than 10% ethanol. There are a few ways to mitigate or eliminate the effects of ethanol, including using high-octane fuel and then only mixing up only enough for the task at hand. One can also purchase 100LL AVGAS at the local FBO, or racing gasoline from a track or speed shop. There are also long-life synthetic fuels being sold under the trade name 50fuel or 40fuel in CONUS (which comes premixed with synth. oil at 50:1 or 40:1) or Aspen in the EU & Canada. These have some favorable characteristics, but come with a high purchase price and small (1qt.) retail packaging. One usually cannot get away with running unmixed fuel. An extremely lucky user might get one tankful of raw gas through the engine, but the rest of us will cook that goose, and soon be shopping at the New Piston Store. A great practice is to add the proper amount of oil to the fuel container at home, prior to fetching the fuel. If one has similar or identical containers, take steps to clearly ID the contents within.

The sawyer needs to inspect and service the air filter every so often (every few tanks, or once a day) Simply pop the cover off, remove the filter, and tap/brush/blow off the debris. Once a year one should probably replace the fuel filter & spark plug.

Maintenance typically requires very little in the way of tools. Normally the bar attachment nuts are 13mm or 19mm, and the chain tension is set with a flat-bladed screwdriver. Stihl equipment has an abundance of T-27 Torx head bolts, while Huskys have an assortment of metric hex screws. Tools are available (which normally come with the unit and tend to grow legs. Two is one, and one is none.) that combine the bar nut & spark plug wrench with a screwdriver or Torx driver. One might need a small flat-blade driver to adjust the idle speed and fuel mixture for operation at varying altitudes. A basic “tune-up” involves nothing more than inspecting, cleaning, or replacing the air filter, spark plug, fuel filter, spark arrestor screen, performing guide bar & chain maintenance, and having a look at the chain drive sprocket wear. Air filter service and chain tension is constant (daily++ inspection & maintenance.) One should regularly clean out accumulated debris from behind the covers & shrouds, and blow out around the engine cylinder cooling fins.

Chains are maintained in the field with properly-sized round hand files or a task-specific bench grinder can be used when the teeth are extremely dull, filed unevenly, or damaged from debris impact. The files are sized for each type/style of cutter, and a flat file is used to lower the rakers down in relation to the cutter. Chain manufacturers sell files with angle and depth guides to assist those new to sharpening chains. Problems with a saw cutting diagonally vs vertical are usually a case of an unevenly sharpened chain. It is also a good idea to flip the guide bar over every so often, so the surfaces get equal wear. This also gives one a 50% opportunity to be chided for having the ‘blade on upside down’.

Problems can arise if the operator has a heavy touch. Forcing the saw through the cut and bogging it down creates a lot of heat within the clutch & drive, and can lead to premature failure of these components. Along these lines, revving the saw excessively with the chain-brake locked will create a lot of unnecessary heat and should be avoided. Saw engines are designed to run at 100% power under load… feathering the throttle in the cut is not good. Also screaming the engine at WOT under no load is a bad practice. If one is checking maximum RPMs with a hand tachometer as part of the tuning process, red-lining the engine has to be done, but one should be brief about it, and avoid excessive no load trigger-happiness.

Since the internal engine bearings and rotating assembly rely on the fuel mix for lubrication, letting the fuel run dry under a load is a bad practice and can lead to a lean seizure. Additionally, any air leaking into the engine (through failing crankshaft seals, cylinder base gasket, or the intake area) can also lead to a piston seizure caused by an overly lean air/fuel mixture. A properly tuned saw engine is crucial for optimum performance and reliability. One who is unfamiliar with setting fuel/air mixture should have their saw ‘tuned’ by an experienced technician at least once during the cutting season.

Storage is pretty simple. If it were to be packed away for long-term, or for shipping, I’d drain & flush out the oil tank, then the fuel tank, then start the saw and let it idle dry. This helps purge trapped bar oil from the passages, and gently runs the fuel in the line & carburetor out. I leave the caps off the tanks for a day or three to purge any vapors. For shorter-term storage, I simply drain the fuel and idle it dry.

Bar oil is specially blended for adhesion and minimizing wear. Used engine or gear oil is not a good substitute for several reasons, including toxicity, and suspended abrasive particles. Virgin automotive or industrial gear oils are better bad choices if that’s all one has available.

If one had a special requirement for a light environmental footprint (cutting adjacent to –or in- a sensitive watershed, such as ones own fish pond) common vegetable oil can be used in lieu of petroleum-based bar oil. There is biodegradable oil available COTS if one had a continuous requirement, but for limited specific use, HH6’s favorite brand will do.

Bar oil is metered out in proportion to the fuel used. Some saws have an externally adjustable oil pump which can increase the flow to accommodate longer bars. Most saws are preset, and often the setting will use one tank of bar oil to one tank of fuel. Filling both tanks at the same time keeps things in harmony, and be mindful which fluid goes where. Bar oil in the front tank and fuel mix in the rear tank is a common arrangement, but be clear on this before you pour. It goes without saying to insure the tank caps are secured after refilling... Stihl's new-style caps are extra-easy to befoul and this leads to oily or flammable messes and a blasphemous operator.

All two-stroke oils are not created equal. Blends for outboards, snowmobiles, and other liquid-cooled engines are not made to the same specification as those designed for air-cooled equipment. I like Stihl HP Ultra at 50:1, a fully synthetic and biodegradable oil designed for saws and other small OPE. Husqvarna XP oil is similar. If one strays too far from the manufacturers recommendations on mix oil, bad & expensive things can occur. JASO FB or API TC/TC+ is a good rating standard to look for when selecting a mix-oil that isn’t OPE specific.

Most, if not all saws currently available are equipped with a baffle or screen to prevent sparks from escaping the muffler. These devices are required to operate a saw or other motorized equipment on public lands, and are a good idea for operation anywhere, especially when conditions for a fire are favorable. Periodic maintenance to the screen involves removing any accumulated carbon or debris. Good quality mix oil and proper ratios drastically reduce carbon build-up. An added benefit to a spark screen is that it prevents mud wasps, or other uninvited guests from taking up residence within the muffler or engine during the off-season.

Chainsaws by design are quite perilous, even when everything is done right. Common sense, proper techniques, education, and familiarity with ones equipment can help minimize the risks involved, but one should be clear that it’s serious business. Thought before action, and constant attention to changing conditions are essential tasks. Basic situational awareness is key.

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