Part I: Spark Plug Basics

Maintenance and Set Up Tips

Replacing of plugs really should be almost as easy as changing light bulbs, however it's not. Bulb replacement does not involve the use of a socket wrench or gapping utilities. A deep socket that fits a plug isn't a suitable spark plug socket. A plug socket has a couple of things that separate it from a deep socket.

The first is a foam rubber insert that pads the spark plug while it is in the socket. Second is the hexagonal part around the top socket. The hexagonal area provides the wrench to set on the socket if there is insufficient space for the ratchet. Motorcycles usually have plenty of space for ratchets and torque wrenches, but the ability to accommodate a wrench on the socket comes in handy for motorcycles with Fat Bob tanks as well as some automotive applications (like a Corvette with headers).

For several years there have been two standard types of plug sockets. 80" Big Twin Evolution and Shovelhead engines require a 3/4" spark plug socket, and Evo Sportsters and Twin Cams need a 5/8" one. And then something took place: spark plugs that required an 11/16" socket came out on the shelves, and 11/16” spark plug sockets are sometimes hard to find. I've seen people fit a short length of foam pipe wrap (the one used commonly in hot water pipes) inside of an 11/16” deep socket to make their own. This procedure is effective and is also an inexpensive solution to improvise an instrument for the person who doesn't replace a lot of 11/16” spark plugs.

Plug Spacing

Spark plug spacing is crucial for accurate firing. Many people assume plugs are already gapped from the factory, which isn't usually correct. Though even if plugs are already gapped, movement when shipped may make the spacing quite a few thousandths inches shorter. Spacing a spark plug isn't rocket science. All it takes are the appropriate tools, some practice, and a little bit of determination.

For starters, pliers and a feeler gauge are not the right tools. Our preferred gapper is the simple, good-old wire-loop tool where every wire loop stands for a distinct size of the gap, and also the metal tabs support a variety of ground electrodes. Our very least favorite may be the disc which has the ramp around the perimeter. The first issue with the disc style is that it puts strain on the center electrode while gapping. Another problem is that one part of the ground electrode might end up somewhat farther out from the center electrode. Screamin' Edge and SplitFire spark plugs, one prong of the ground electrode can be higher than other plugs.

Focusing on 3 straightforward procedures will allow you to correctly gap plugs. Initially, don't try to bend the center electrode. Second, never bend the ground electrode laterally. Utilize the spacing tool to slowly push the tip of the ground electrode near or farther from the tip of the center electrode. Additionally, check the gap by working out the correct wire loop in between the gap. The spacing is right when you feel a slight amount of friction when the wire moves in the gap.

Changing Spark Plugs

Just before the removal of a plug, wait until the engine has cooled down, and then start using a shot of compressed air to clear out dust and dirt away from the space around the spark plug. A ratchet and a spark plug socket are my desired utilities for this section of the process. Upon cautiously taking off the spark plug wire by pulling on the boot, not the wire, I remove the aged plug with a ratchet and plug socket by turning them counter-clockwise.

When the worn out plugs are finally out, it is time to mount the correctly spaced plugs. Start out by putting a tiny amount of lubricant on the threads for each plug. Current Harleys have aluminum heads and spark plugs have a steel shell. Repeated heating and cooling of the cylinder heads may cause a chemical reaction from the steel spark plug shell and the aluminum cylinder head. This results in an effect like it has been welded.

Soon after applying the lubricant oil around the spark plug threads, begin winding the spark plug clockwise into the head working it with your fingers rather than a ratchet and plug socket. A best practice that lowers the possibility of getting a cross threaded plug and the costly damages that may occur.
After the brand new spark plug is finger-tight, reach for the torque wrench and spark plug socket. The torque spec for spark plugs in a TC 88 is 11-18 ft-lbs., so split the difference and go for 15 ft-lbs.

By doing this, if the torque wrench turns out to be off with no reason in mind, you will still be within the recommended spec. Is the right torque critical for spark plug installation? Typically, indeed yes! If the spark plug is too loose, heat exchange to the head may be reduced, while the plug may overheat. If a spark plug remains not tight enough, it possibly can work its way out from the head due to vibration and combustion pressure. And that is very harmful. Insufficiently tightened spark plugs are also held responsible for combustion chamber debris finding their way into the threads of the spark plug hole.

On the other part, turning plugs too tight can cause other problems. If a spark plug is tightened too much, the chances are it'll be harder to take out. Over tightening may also crush the gasket on the gasket seat plug. Over tightening can harm the threads in the head and has been the suspect in the gap distorting.

Without having a torque wrench, get the fresh plug tightened using the finger and utilize a ratchet to carefully tighten the plug another quarter to half a turn. This approach is certainly a lot less accurate as compared to utilizing a torque wrench, but it can get you somewhere in the 11-18 ft-lbs. limit.

This season, bike runs are going to kick off all throughout the US. The vast majority of motorcyclists will undoubtedly be congregate for one week long festivity all expressing their love for bikes. You will hear a number of stories and building tips to chat about with brand new friends while you ride the time in the rally. Be sure to ride safe and put on the necessary safety equipment like carbon fiber helmets. Best of luck and have a wonderful ride.