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Author and Copyright

Author: Samuel M. Goldwasser

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  • Starting the mower

    Most mowers and other small pieces of gas powered yard equipment use a self retracting recoil type starter. You pull on a handle attached to a cord wound around a one-way clutch affair. Pulling on it rotates the engine's crankshaft and the clutch allows the engine to run without pulling you back into the mower! If yours has an electric starter, then you don't need to tug on anything - plug it in and push a button or turn a key. Of course, finding an outlet at the far end of a large yard may prove to be a challenge. With larger equipment like riding mowers, power is usually provided by an on-board rechargeable battery. In either case, there will be some kind of backup recoil or rope starter should the electric start be unusable or inconvenient.

    For the following, we will assume you pull a self-retracting starter rope. With an electric starter, replace the words: 'pull...times' with 'crank for several seconds'.

    Move the mower or other equipment to the place where it will be used - no sense in dragging a chugging lawn mower through the neighborhood. Position it on a solid level surface. Make sure there are no loose stones, twigs, branches, logs, etc. underneath to get sucked up and thrown about once you succeed in getting the engine started (if you ever do).

    When attempting to pull on the starter cord, it may be helpful to put one foot on the mower deck to brace it. Whether this is needed will depend on the design of your mower and in what direction the cord exits from the starter.

    You or the starter motor supplies the power to get it started. However, at the low speed of starting, special modifications may be required to the fuel system for the engine to catch. These may take one of the following forms:

    If the appropriate procedure is not successful, the engine may be flooded. You can give it 15 minutes or so for the gas to evaporate and try again or, if there is an IDLE or LOW speed position, open any choke and pull the rope several times in this position which should clear out the excess gas. Then repeat the recommended starting procedure.

    Blade sharpening

    The blade in a rotary lawn mower doesn't need to be sharp as a carving knife or scalpel but serious dents and nicks will result in a less than perfect lawn (to say the least!). In addition, a seriously unbalanced blade can result in excessive vibration and eventually, possible internal damage as well.

    First, drain the gas or remove the gas tank. If you will be filing steel, you get sparks. Sparks are not the greatest thing to have around gasoline vapor. Enough said. Disconnect the spark plug wire and tie it safely away from the spark plug or remove the spark plug entirely. Turn the mower on its side.

    CAUTION: Immediately check for oil leaks at the oil filler pipe or elsewhere. If there are any, you will need to work on the mower just propped up by 45 degrees or so. Or, use this as a good excuse to perform an oil change and drain the oil (even if the engine is cold, most of the oil will drain out but it will take a little longer). Just don't forget to refill the crankcase with fresh oil once you have completed work on the blade!

    Check that the blade isn't bent. Locate a reference point on one side and note the height of the blade tip at that location. Rotate the blade 180 degrees and check the height of the opposite blade tip. There should be no significant difference - say no more than 1/8" or so. If it is greater, the blade is bent or the crankshaft is bent. Either will require further investigation as running the mower under such conditions will probably result in excessive vibration and can be dangerous.

    Assuming this is fine, inspect the blade:

    Slight nicks and dents can be cleaned up with a file while the blade is still installed on the mower. Unless you have run into a curb, this is probably all that is needed on an occasional basis. Removing this small amount of metal will also not unbalance the blade enough to worry about. Refer to the section: Non-violent blade removal if it needs to come off the mower.

    If the damage is severe, consider replacing the blade entirely - they are not that expensive (usually under $10). Otherwise, you can use a file, a bench grinding wheel, or a grinding wheel mounted in an electric drill (there are special attachments for this specific application).

    Since the rotating blade also contributes to the proper air flow, you do not want to upset the shape. Grind in such a way that the original blade angle is preserved. It doesn't need (or want) to be razor sharp. A 1/64" edge is fine. Anything finer will quickly be dulled by little bits of stone and dirt in any case. Safety is not the main concern here - if any part of your anatomy contacts the whirling blade, you WILL be in trouble no matter how dull or sharp the blade might be!

    Attempt to remove approximately equal amounts of metal from both ends and in roughly similar areas if possible. If there are a few large nicks, it isn't necessary to remove them completely - your lawn (and neighbors) will never know the difference.

    Check the balance by positioning the blade at the center hole location on a pencil or other rod - you don't need a fancy blade balancer but can use one if you like. If it tips one way or the other, remove more material from the heavy side a little at a time.

    Replace the blade along with all its mounting hardware. Make sure you get all parts in the same relationship as they had originally. The blade must have its sharpened edges pointing downward. Don't forget the install the key if it is separate and DO NOT substitute a hard steel key for the soft metal one that should be used. See the section: Why soft metal keys must be used. If the locking key or blade adapter key appear damaged in any way, replace it.

     

    Lawn mower will not start

    This is probably the most common problem you are likely to encounter. The cause is very often the same - lack of maintenance.

    Note that the assumption here is that it cranks - the crankshaft and blade rotates in a normal manner but the engine never catches. Some larger (Briggs and Stratton) engines may have a low-oil cutoff switch which will stop the engine if the oil level is inadequate. However, this is not likely on a push mower.

    If you are unable to pull the cord (or the auxiliary starter on one with electric start), there may be a clump of grass stuck between the blade and the deck or there could be serious internal damage, especially if you just encountered an immovable object. See the section: Lawn mower will not start after the blade hit an obstruction. However, you didn't forget to engage the dead-man bar, did you? On most inexpensive mowers this safety interlock is needed to both enable the ignition system and release the blade brake.

     

     

    Lawn mower too loud

    Small engines - especially those on cheaper mowers - are usually loud, no question about it. However, if yours sounds like it is about to explode or take off, there may be something actually wrong.

    Obviously, if it is backfiring every other stroke, you have a problem with the ignition timing, mixture, valves, etc. What this section deals with is just the normal noise assuming the engine runs properly - and how to reduce it. Else, you need to perform the proper maintenance first.

    Note that for a 2 stroke engine, the muffler is particularly critical for proper operation and substitution may be more difficult.

     

    Types of rotary mowers

    In addition to options with respect to gasoline or electric power, rotary mowers can be classified based on such things as: walk-behind vs. ride-on, to bag or not to bag, and rear or side discharge or mulcher: WARNING: Most lawn mowing accidents result from reckless or careless use of riding mowers and lawn tractors, not walk-behind mowers. These are not as stable as an automobile especially when their large bags are full of heavy, wet, grass clippings and may tip over on inclines that would not be a problem with someone in control of a walk-behind lawn mower. They are best and safest for use on large flat open lots. A walk-behind mower - perhaps even a manual reel mower - should be used for sloping or irregular areas and for mowing or trimming around obstructions like trees, shrubbery, landscaping timbers, posts, fences, planters, boulders, and so forth.

    About engine oil

    For the common 4 stroke engines such as Briggs & Stratton or Tecumseh, you don't need to buy specially high priced engine oil. The type likely used in your automobile will work fine and will be much less expensive. Although small engine manufacturers may recommend SAE 30 oil, they usually also state that 10W-30 or 10W-40 are acceptable substitutes - and these are what your car probably uses. New oil should have at least the SG rating though if you have some SF in your garage, that will be fine also (for your lawn mower, not your car!). However, there are situations like equipment that must run in extremely cold weather (probably not a problem with grass mowing!) where specific alternative oil recommendations should be followed.

    Rotary mowers

    These may be gasoline or electric (AC line or battery) powered. A spinning blade or blades whirls at the selected cutting height and lops off the tops of you grass by side impact. This is most definitely brutal treatment of your poor defenseless grass! The length of the cutting blade determines how much of a swath is cut on each pass - typically 18 to 24 inches for a walk-behind mower; up to 36 inches or more for a riding mower. Mowers with large swath widths may use two or more smaller blades instead.

    The uniformity, consistency, and just general appearance of a lawn mowed with a rotary lawn mower is not quite up to the standards of that of a professional reel mower. You will never get the perfect manicured look though some models may come close. However, the simplicity, lower cost, and need for less and more easily performed maintenance will generally overcome the desire for perfection unless your lawn is featured regularly in "Better Homes and Gardens" magazine.

    Gasoline powered rotary lawn mowers are by far the most common type used by homeowners and many professional landscapers as well. Most walk-behind mowers use a manual recoil (pull) starter though electric start is available on more sophisticated (and more expensive) models and generally standard on riding mowers and lawn tractors.

    The main disadvantages of a gasoline powered mower are the need to deal with the handling and storage of gasoline and routine engine maintenance at the end of the mowing season to assure easy starting next season and to prolong engine life. However, most of this is pretty straightforward. See the section: General preventive maintenance. Small gasoline engines also do contribute to air pollution but new mowers must meet more stringent EPA requirements as of September, 1996.

    Electric rotary mowers are also available in both plug-in and cordless (battery powered) versions. However, since gas mowers are generally more powerful and not limited by the length of a power cord or charge of a battery, they continue to dominate the market. Electric mowers are, of course, non-polluting but the electricity had to be generated somehow.