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Spark Plug Essentials

By Darnell Austria


Maintenance and Install Guidelines

Replacing spark plugs really should be nearly as easy as changing lamps, but it's not. Bulb changing doesn't require using a socket wrench or gapping utilities. An extended socket that fits a plug isn't a correct plug socket. A spark plug socket has two things that differentiate it from a deep socket.

The first is a foam rubber fit that cushions the plug while it is in the socket. Second is the hexagonal part around the top socket. The hexagonal area allows a wrench to fit on the socket when there's insufficient room for a ratchet. Bikes usually have plenty of clearance for torque wrenches or ratchet, and yet the capability to support a wrench to the socket is useful for motorcycles with Fat Bob fuel tanks and a few automotive uses (like a Corvette having headers).

For many decades there were two standard types of plug sockets. Shovelheads and 80" Big Twin Evolution engines need a 3/4" spark plug socket, and Evo Sportsters and Twin Cams need a 5/8" one. And then some thing occurred: spark plugs that required an 11/16" socket where available on the market, and 11/16" plug sockets are often difficult to find. We've heard individuals put a short length of foam pipe wrap (the product that's often used to insulate hot water pipes) inside of an 11/16" deep socket to use by their own. This method works and is an inexpensive solution to improvise a tool for the person that doesn't replace a lot of 11/16" plugs.

Spark Plug Spacing

Plug spacing is essential in getting accurate firing. A lot of people assume spark plugs are already gapped at the factory, which is not often true. And yet even when plugs are pre-gapped, activity when being shipped can make the space quite a few thousandths of an inch smaller. Spacing a plug is not too difficult. What in only needs is the ideal tools, quite a few practice, and a bit of dedication.

To begin with, feeler gauge and pliers usually are not the right tools. My favored spacing tool is a good, old wire-loop tool where every single wire loop stands for a different gap size, and also the metal tabs accommodate distinctive ground electrodes. Our least favorite is the disc with the ramp around the perimeter. One problem with the disc style is that it puts stress on the core electrode when gapping. The other issue tends to be that the other side of the ground electrode may end up a bit further out from the center electrode. Screamin' Edge and SplitFire spark plugs, 1 prong of the ground electrode could be a bit higher than the other.

Observing three simple guidelines will assist you to correctly gap plugs. Initially, do not bend the core electrode. Next, never ever flex the ground electrode laterally. Work with the gapping tool to carefully move the end of the ground electrode near or farther away from the tip of the core electrode. Finally, examine the gap by moving the appropriate wire loop through the gap. The spacing is correct when you sense a slight amount of friction when the wire moves through the gap.

Replacing Spark Plugs

Just before removing a spark plug, ensure that the motor has cooled down, and then use a shot of pressurized air to clear out dust and dirt from the space around the spark plug. A ratchet and a spark plug socket are my preferred tools for this particular part of the process. After gently detaching the spark plug wire by drawing on the boot, not the wire, I remove the worn out spark plug with a ratchet and plug socket by rotating them counterclockwise.

When the old plugs are out, you're all set to set up the appropriately spaced spark plugs. Start out by putting a small amount of anti-seize lubricant on the threads of each plug. Modern day Harleys have aluminum heads and spark plugs have a steel shell. Repeated cooling and heating from the cylinder heads may trigger a chemical reaction involving the aluminum cylinder head and steel plug shell. This results in an effect like it has been welded.

Soon after applying the lubricant (anti-seize) around the spark plug threads, begin turning the spark plug tighten manner to the head using your fingers rather than using a spark plug socket or ratchet. A best practice that lessens the possibility of getting a spark plug that is cross threaded and the pricey damage that may occur. Once the brand new plug is finger tight, reach for the plug tools, the torque spec for plugs in a TC 88 is 11-18 ft-lbs., so split the main difference and opt for 15 ft-lbs.

That way, if the torque wrench turns out to be off for some reason, you will still be within the recommended specification. Is proper twisting vital for spark plug fitting? It's really simple, indeed yes! In cases where the plug is a bit loose, high heat exchange in the head may be minimized, and the plug could overheat. Whenever a spark plug remains not tight enough, it possibly can find its way out from the head caused by vibration and combustion pressure. And that is certainly very harmful. Loose spark plugs have been held accountable for combustion chamber debris showing up in the threads of the spark plug hole.

At the other extreme, turning plugs excessively tight will cause other problems. If a spark plug is over tightened, it's likely that it'll be tougher to remove. Over tightening may also grind the gasket within a seat plug. Extreme over tightening can damage the threads within the head and has always been the cause of deterioration.

Without a torque wrench, make the new spark plug finger tight and utilize a ratchet to carefully tighten the spark plug another quarter to half a turn. This method is certainly a lot less precise as compared to having a torque wrench, but it will give you anywhere in the 11-18 ft-lbs. limit.

This season, bike runs will kick off from all over the country. The vast majority of motorcycle drivers will undoubtedly be assembling for 1 week long festivity all expressing their fascination with bikes. You will hear a number of tales and building tips to chat about with new friends while you drive the days with the bike week. Make sure to ride safe and wear the required safety equipment like carbon fiber helmets. Good luck and have a wonderful ride.




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