Saturday, October 19, 2013

Spark Plug Replacement on a Harley Davidson Street Glide

This is going to be a short post and its one of those stand bye posts that Ill pull from the closet when life is busy. We started a new construction project at work so for the next 6 weeks I probably wont get a weekend off to write about much.

SPARK PLUGS! Another super easy maintenance task! The service manual schedule lists this to be performed at 30K miles. You will need a couple, literally 2, special tools for this. The tools are not expensive and easily obtainable. Not only that but you will be able to use these 2 tools on your car as well! Dual purpose! Or in my case quad purpose having 2 SUV's and 2 bikes.

For changing spark plugs you will need a spark plug socket and a gap tool/gauge. You can get the tools at Autozone or for that matter any auto supply shop. You'll need to be sure to get a spark plug socket. These are a bit different from a standard deep socket. It will have a rubber insert in the top portion of the socket. The rubber is put inside to keep the metal sides of a standard socket from chipping or cracking the porcelain on the top part of the spark plug. It also grabs the socket which makes it easier to remove from the cylinder once you've got the spark plug loose.

The spark plug gauge is used to measure the correct gap for the firing of the plug. Though this is important, its not as critical as you might be concerned about seeing as the gap measurement for my stock Street Glide is .025-.038. That is a huge range to have available and very easy to achieve with a gap tool. Not that I would do this since I have the tool but that range is so big you can almost eyeball the correct gap.

I purchased Screaming Eagle spark plugs from our local dealership. Go to the parts counter and let them get the plugs for you based on the year and engine in your bike. They will also ask you if you have engine mods such as a stage 1. This will determine what plugs you need. The plugs are different so you want to be sure to get the correct ones. Pick up a tube of thread anti-seize stuff too. This will help prevent the plug threads from rusting or seizing from carbon in the cylinder for the next change out.

Gently pull the sparkplug cable off to reveal the plug. Get that sparkplug socket out and put it on making sure you feel the rubber inside the socket is secure on the plug. Remove the plug and inspect the end. The color will give a very good indication to how your engine is running. The following assessment is a consolidated explanation, your service manual will provide more details.

1- A wet black and shiny deposit indicates an oil fouled spark plug.
2- A dry fluffy or sooty black deposit indicates an air fuel mixture that is too rich
3- A light brown glassy deposit indicates an overheated sparkplug caused by a lean air fuel mixture.
4- White, yellow, tan or rusty brown powdery deposit indicates balanced combustion.

Get one of the new sparkplugs and set your gauge tool anywhere between .025 and .038 and stick it between the sparkplug contacts. If it doesn't fit, softly grab the contact with a pair of pliers and bend it up a bit until you can get the gauge in between. If its too loose you can very lightly tap the end on a towel on a solid surface until the gap is correct. You'll want the gauge to fit snugly between the contacts and touch both sides.

Now wipe a bit of the anti-seize lubricant on the threads and put it back in using your hand at first to make sure your not cross threading the plug into the cylinder. Once you cant turn it with your hand anymore use the sparkplug socket again and tighten. This is kind of important, you have to be careful not to over tighten the plug.  If you do and ream out the cylinder threads your gonna be in a world of hurt and out of a lot of money to replace the top of your heads.  You don't have to use a torque wrench but if you have one use it and tighten the plugs to 12-18 foot pounds as indicated by the service manual.

Inspect the cables for cracks and if their ok put them back on. You might hear or feel a slight snap as the contact engages with the top of the plug. This will help you to know if its on all the way.  That's it!  A simple quick maintenance task that will save you a few bucks and again help you know whats going on with your bike.





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