Engine number is 143804092 and the spark plug is Sears PM4, which is equivalent to Champion JC8
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The Craftsman 4.5hp mower uses either a Champion model RJ19LM or J19LM spark plug, or equivalent, with the gap set at . 030 inch.
The gap between the spark plug`s center electrode and outer electrode should be set at 0.02 inch, or 0.5 millimeter, for most Husqvarna trimmer models.
The gap setting is different for each vehicle but most are somewhere between 0.028″ and . 060″. Consult the owner`s manual or Champion ® catalog to find the recommended setting for the vehicle you`re working on.
A: This spark plug should have a gap set to 0.02 inches.
One of the key factors that makes a spark plug work well, or not, is the size of the gap between the electrodes. If the gap is too small, the spark will likely be too weak and cause the engine to run poorly or with poor efficiency.
Checking and Gapping the Spark Plug
The gap, or distance between the electrodes, should be between 0.028 and 0.031 inches. Check the gap with a gap gauge and adjust the ground electrode until the gap falls between the two numbers.
The larger the gap, the more voltage is needed to jump the gap. Most experienced tuners know that increasing the gap size increases the spark area exposed to the air-fuel mixture, which maximizes burn efficiency.
A smaller gap will yield a short, intense spark and will usually make the engine real responsive. A wide gap creates a longer spark arc but without sufficient “juice” from your ignition system, (including amps), it can be weak and yellow in color.
But if the spark gap is too small, there won`t be enough room for the airfuel mixture between the ground electrode and center electrode. So when the spark plug fires, there`s a possibility that nothing ignites. A wide gap between the center electrode and ground electrode allows for a strong, clean burn.
Blisters on the insulator tip, melted electrodes, or white deposits are signs of a burned spark plug that is running too hot. Causes can include the engine overheating, incorrect spark plug heat range, a loose spark plug, incorrect ignition timing or too lean of an air/fuel mixture. The spark plug should be replaced.
As the spark plugs wear, the spark plug gaps widen, also weakening MPG. This is because the wider the spark plug gap, the more voltage is required to arch between the electrodes. The smoother the combustion process, the lower the demand for engine power and the lower the demand for fuel.
Knowing the lawn mower spark plug size is essential when you need to replace damaged ones. However, some spark plugs can vary in size due to their manufacturer`s specifications. Using the incorrect spark plugs can have dire consequences for your mower.
Gapping fine-wire spark plugs
While most NGK spark plugs are pre-gapped, there are occasions when the gap requires adjustment. Care must be taken to avoid bending or breaking off the fine-wire electrodes. NGK recommends a round wire-style or pin gauge gap tool to measure the gap.
NGK do not recommend gap adjustment for precious metal spark plugs.
A spark plug gap is kept from– 0.3-0.7 mm because 0.3-0.7 is perfect gap for making spark in spark plug.
On the other hand, a larger gap gives a “hotter” or “fatter” spark and more reliable ignition of the fuel-air mixture. In addition, a new plug with sharp edges on the center electrode will spark more reliably than an older, eroded plug.
The spark plug gap widens bit by bit as the electrode wears, so high discharge voltage becomes necessary and misfire occurs more easily.
If a spark plug is too long, it can protrude into the combustion chamber and hit the piston or a valve. This could not only shatter your spark plug into the piston, but shatter the piston itself or damage the head. A spark plug that is too short will cause your engine to buck.
The most common sizes of spark plug nuts and the sockets used to remove/install them are 15/16″, 13/16″ and 5/8″. These tools are available individually or in sets at most automotive parts supply, hardware and other tool supply stores.
The recommended spark plug gap for a Honda GCV160 engine is 0.028″– 0.030″.
3/8-in Drive 13/16-in Spark Plug Socket | CRAFTSMAN.
Champion RC12YC Spark Plug, 0.032 to 0.038 in Fill Gap, 0.551 in Thread, 5/8 in Hex, Copper, For: 4-Cycle Engines.