Vehicle Spark Arrestors
Ralph H. Gonzales, Mechanical Engineer
For a vast majority of users, part of the enjoyable experience is being in the outdoors while operating an OHV. Because this activity commonly takes place in areas that are in close proximity to fuel sources, spark arresters are required on OHVs where fire is a threat.
The term “passenger vehicle” can encompass a wide range of motor vehicles. Most State vehicle codes differentiate between vehicles used for transportation and those used for recreation purposes. Dune buggies, motorcycles, and all-terrain vehicles (ATVs) are required to meet spark arrester regulations because they are not considered passenger vehicles.
Spark arrester laws vary from State to State. OHV operators should consult their State’s policy.
The following are some of the
most commonly used OHVs that require spark arresters.
Spark Arresters Work
Various methods are used to clean accumulated carbon particles out of a spark arrester. Some include a cleanout plug, end cap, cleanout plate, inserts, snap rings, cleanout bands, and Allen bolts. The spark arrester must be serviceable without removing the complete exhaust system.
The cleanout requirement is one of the most critical elements of the trap arrester. It is also one of the most often ignored. During inspections, owners must be reminded that this type of arrester requires regular and timely maintenance, a critical element of spark arrester effectiveness.
Some models of spark arresters/mufflers require fiberglass packing. This packing should be replaced every 30 hours. Evidence of exhausted packing includes oil dripping from the exhaust tail pipe and/or excessive noise. Fiberglass is the only approved qualified packing.
for OHV Spark Arresters
Many people think that a muffler/silencer is also a spark arrester. Mufflers and silencers are only designed for noise control. Only an inspection can determine whether this is a spark arrester or a muffler/silencer.
If the OHV has been operating, beware of very hot metal in and around the exhaust system. The arrester will be a chamber-like device located somewhere along the exhaust discharge. Find the manufacturer’s name or logo and the model number located on the spark arrester. It may be necessary to clean a portion of the arrester to reveal that information. It can usually be found on an attached metal plate. The words “USDA Forest Service Qualified,” “Spark Arrester,” or “Qualified” stamped on a piece of equipment does not guarantee that it is a tested and qualified arrester.
With the engine off, and using a penlight, look into the spark arrester to visually ensure that the interior has not been removed or altered. You may be able to see the interior section that deflects the exhaust. Use a narrow rod, such as a 8-in wooden dowel, to gently feel for the internal parts of the arrester. Check how far you are able to insert the wooden dowel internally and cross check this measurement with the outside of the spark arrester/muffler. This will indicate whether you are able to pass the dowel the length of the arrester/muffler. If you are able to pass the dowel the total length, it is not a qualified arrester.
All trap spark arresters have internal fins or louvers that deflect the exhaust. If you suspect that an arrester may be altered, have the owner take the arrester apart for further inspection. Although the arrester/muffler may have the approved model number and the manufacturer information stamped on the shell, the inside components of the spark arrester mechanism may have been removed. Only through a thorough inspection can this type of modification be noted.
Arresters can be modified to avoid routine maintenance or to give the false perception of improved engine performance. Some modifications that have been detected include complete or partial removal of the spark arrester component parts, perforation of an arrester part, and installation of foreign objects into a muffler silencer, “mocking” spark arrester parts when a wooden dowel probe is used. Examples of these foreign objects are washers, bottle caps, and steel wool.
Owners must be aware that spark arrester laws include the term “in effective working order.” Spark arresters need to be periodically cleaned to eliminate the trapped particles of carbon. The same conditions that cause spark plugs to foul can also cause a spark arrester to become inefficient. If it is not maintained, then its performance is hampered and it is not considered a legal spark arrester.
There are two volumes of the guide: General Purpose and Locomotive, Volume 1, and Multiposition Small Engine, Volume 2. A revision of the guide is published every year. Therefore, each volume is published every 2 years. An online guide, updated every quarter, is available on the USDA Forest Service Intranet at http://www.fsweb.sdtdc.wo.fs.fed.us. It is a searchable database that allows the user to make powerful searches.
Attn: Spark Arrester Program
Leader or http://www.fsweb.sdtdc.wo.fs.fed.us
Project Leader, Fire Management
San Dimas Technology & Development Center
444 East Bonita Avenue, San Dimas CA 91773-3198
Phone 909-599-1267; TDD: 909-599-2357; FAX: 909-592-2309
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