NGK Spark Plug CMR6H 3365

Product Information

As a general guideline, among identical spark plug types, the difference in tip temperature from one heat range to the next is approximately 70°C to 100°C. Spark plugs are a key part of maintaining a petrol power tool, especially STIHL chainsaws, and you may think that one spark plug is much the same as another. A standard NGK spark plug and NGK spark plugs sold by STIHL may have the same part number stamped on them, but the STIHL NGK spark plug has some key differences.

The heat range must be carefully selected for proper spark plug thermal performance. If the heat range is not optimal, then serious trouble can be the result. The optimal firing end temperature is approximately 500°C (932°F) to 800°C (1472°F). The two most common causes of spark plug problems are carbon fouling (< 450°C) and overheating (> 800°C). This spark plug has a resistor that is produced with a glass and carbon mixture, which is fired to ensure superior performance and durability. It has corrugated ribs that prevent flashover and cold rolled threads to inhibit damage to the cylinder head. The NGK Standard Spark Plug is constructed from durable material that is corrosion and abrasion-resistant. The spark plug insulators are made of 99 per cent pure alumina silicate, providing longer insulator noses for reduced fouling.Pre-ignition occurs when the air-fuel mixture is ignited by a hot object/area in the combustion chamber before the timed spark event occurs. Pre-ignition will dramatically raise the cylinder temperature and pressure, which can melt and hole pistons, burn valves, etc.

A misfire occurs when the spark travels the path of least resistance instead of jumping across the gap. Misfires can be caused by the following: The spark plug firing end temperature must be kept low enough to prevent pre-ignition, but high enough to prevent fouling. This is called “thermal performance,” and is determined by the heat range selected. It is most often caused by the wrong (too hot) heat range spark plug, and/or over-advanced ignition timing. An improperly installed (insufficient torque) spark plug can also result in pre-ignition due to inadequate heat transfer. Stihl: BG56, BG66, BG86, SH56, SH86, BR200, BR500, BR550, BR600, BR700, BT131, FC56, FC70, FC90, FC95, FC100, FC110, FS25, FS40 (Ø10mm Plug engine only), FS50, FS56, FS65, FS70, FS56 (Ø10mm Plug engine only), FS87, FS89, FS90, FS91, FS94, FS100, FS110, FS111, FR130, FS130, FS131, FS240, FS260, FS310, FS311, FS360, FS410, FS460, FS460 C-EM, FR410, FR460, FR480, MS150, MS150 C-E, MS170, MS171, MS180, MS181, MS181 C, MS192 C-E, MS193C, MS193T, MS201, MS211, MS211 C, MS231, MS241, MS251, MS241 C-M, MS362, HT100, 101, 130, 131, KM56, KM90, KM94, KM100, KM111, KM110, KM130, KM131, HL90, HL91, HL94, HL95, HL100, HS81, HS86, HS46, HS46 C-E, HS46, HS56, HS56 C-E, HS81, HS82, HS86, HS87, HT56, HT100, HT101, HT102, HT103, HT130, HT131, HT132, HT133, MS 201 T, MS 201 TC, SH56, SH200, SR200

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There are many external influences that can affect the operating temperature of a spark plug. The following is a brief list to consider in avoiding reduced performance and/or expensive engine damage. Engine Speed and Load Husqvarna: 345FR, 439, 526XP, 545, 545FX, 545FXT, 545RX, 545RXT, 550XP, 550XPG, 555, 556, 560XP, 560XPG, 562XP, 562XPG, T435, T540XP, T540XP 11 Air (atmospheric) pressure and cylinder pressure decrease as altitude increases. As a result, spark plug tip temperature will also decrease. The union nut (1) of a STIHL spark plug is fixed in place. This ensures there is no spark gap which could impair performance or potentially ignite gasoline fumes.

This spark plug features a triple gasket sealing process that eliminates fuel leakage. It also comprises a solid copper core that gives superior heat dissipation and conductivity. The main differences between the STIHL NGK spark plug (right) and the off the shelf NGK plug (left) are: As the air temperature or humidity increases, the air density decreases, requiring a leaner air-fuel mixture. If the air-fuel mixture is too rich, decreased performance and/or carbon fouling can result.This spark plug has a resistor that is produced with a glass and carbon mixture, which is fired to ensure superior performance and durability. It has corrugated ribs that prevent flashover and cold rolled threads to inhibit damage to the cylinder head. Features & Benefits: The primary function of the spark plug is to ignite the air-fuel mixture within the combustion chamber under any operating condition. Illustrations may differ slightly from original product and are not assembled, but in boxes for shipment. If an air-fuel ratio meter or gas analyzer is not available, it will be necessary to visually inspect the spark plugs frequently during the tuning process to determine the proper air-fuel mixture.

A colder heat range spark plug may be necessary due to the increased cylinder temperature as boost pressure (manifold pressure) and subsequent cylinder pressure and temperature increase. A hotter heat range spark plug has an insulator design with a longer heat flow path to the metal shell of the plug. As a result, more heat stays in the ceramic firing end and less is dissipated to the engine. A colder heat range spark plug has an insulator design with a shorter heat flow path to the metal shell of the plug. As a result, less heat stays in the ceramic firing end and more is dissipated to the engine. For a spark plug to function properly, it must have a tip temperature high enough to burn off carbon deposits (self-cleaning) and avoid fouling, while remaining low enough to avoid overheating the ceramic firing end and pre-ignition. One of the most misunderstood aspects of spark plugs – is the heat range. One misconception is that the heat range is related to the spark temperature or intensity. Another common misconception is that the spark plug is designed as a heat sink to “remove” heat from the combustion chamber. These ideas are both false. The spark plug is heated during combustion and must dissipate that heat to the cylinder head at a certain rate to avoid overheating the ceramic firing end. The spark plug heat range only indicates the rate that the spark plug dissipates its firing end heat to the engine.Interference suppression resistance (2) is tuned to STIHL machines for the optimal spark and efficiency. This protects the machine’s ignition module from early failure. Spark plugs must provide a path and a location for electrical energy from the ignition coil to create a spark used to ignite the air-fuel mixture. A sufficient amount of voltage must be supplied by the ignition system to spark across the spark plug gap. This is called “electrical performance.”