Introduction

The stock coils are prone to leaking so much spark that some riders have observed large arcing from their coils to the frame or tank on a dark night. Yikes! As a result, many owners have wrapped their coils with electrician's tape--an adequate, if un-elegant, solution.

Idiot Disclaimer: Do not run your engine in an enclosed space to achieve darkness. Do not touch coils or sparkplug wires while the engine is running.

I wrapped my coils with electrical tape several years ago, and it did seem to help smooth the idle a bit. But then I read that many owners were tracing various engine difficulties--especially plug fouling and carbon build-up--to sparkplug wire issues. It was discovered that the stock wires have excessively high electrical resistance. In fact, owners that modified their stock plug wires reported easier starting, smoother idle, and less carbon build-up. The stock sparkplug wires are built right into the coils, so you can't replace the the wires without also replacing the coils. When Nemesis Racing announced their introduction of high performance coils and plug wires, I decided it was time to replace mine. There are two, primary, options for aftermarket coils for the Road Star:

• Dynatech, (Dyna Performance Electronics, Glendora, CA)
• Nemesis Racing, (Nemesis Racing, g_wicks@bigpond.net.au, Australia, or powdercoatka@aol.com in North America.)

I opted for the Nemesis ones, as I have had excellent results with their other products, and, though I am not an electrical guru, I knew that matching component specs was important. Here's what Joel (Odo) Parker (Road Star Clinic author, and professional Yamaha mechanic) has to say:

"Our coils are rated at 1.53 ~ 2.07 ohm resistance, (99 to 03's), so, getting that rating right in there with how our systems work, is essential. The Dyna coils for our R*'s are 2.2 ohms, (A little too high). The Nemesis coils are 1.5 ohms, ('JUUUSSSTTT' right. :-)). More spark for the system.”

• Nemesis or Dynatech coils
• Nemesis (or other, low resistance) sparkplug wire set
• Sparkplug nipple tops--quantity: 4. Required if using Nemesis sparkplug wires. Check with your supplier if you'll be using wires from other sources. The nipple tops are little screw-on tops that allow you to use standard, automotive plug wires. You know--the ones that come, loose in the box, with each new sparkplug.
• Dielectric (silicone) grease, to help reduce corrosion in electrical connections.

Tools

• 10mm box, or open end wrench
• Modest metric socket wrench set, optional
• Needle nose pliers.
• Screwdriver, slotted (--)
• Sharp knife or razor-knife

Planning Coil Placement

Before diving in to the project, you must give some thought to coil placement. I opted to keep my coils in the stock position, but they can be mounted just about anywhere. Some owners have built or purchased brackets to mount their coils between the cylinders on the left side, after they moved or eliminated their fuel pump. (see photo example below). These mounts can be hand built, or they can be purchased from several online suppliers.

Getting Down to Business

Remove the tank. Disconnect the positive battery cable.

The stock coils are attached to the frame, above the front cylinder. Unless your bike has been modified, and coils switched for some reason, the left coil feeds both sparkplugs of the rear cylinder, and the right coil feeds the front cylinder.

Next, make note of, or photograph, the routing of the plug wires for both cylinders. You won't be able to exactly copy this routing with the new coils, but knowing how the stock wires are run can give you greater confidence in routing your new ones.

I suggest replacing one coil at a time, so wire connections are not confused, even if you get interrupted.

The procedure is not quite the same for both coils. We'll do the left side first.

Begin removing the left-side, stock coil by unplugging the two sparkplugs of the rear cylinder. Then open or cut any wire-ties that are holding the plug wires to the frame.

Next, disconnect the two little wires from the left coil. You don't have to keep track of which wire goes where--as long as you keep the wires for the left coil from ending up on the right-side coil.

Now unscrew the little bolt at the coil's forward end.

The coil and plug-wire assembly can now be removed. Do this by swinging the bolt-end of the coil away from the bike enough to allow you to wiggle the other end forward and out of its rubber mount.

Set the coil assembly aside.

Remove the rubber mount from the rear bracket (photo above). Clean it. Then use a sharp blade to slice an 'X' through the flat back. This will enable the long end of the new coil to pierce through the end of the rubber mount.

Tip: Actually, I sliced the flat back of the rubber mount completely out. This made it a little easier to slide the coil in, I think. But it also made the rubber mount prone to coming out of its seat when I tried to work the new coil in.

Now lubricate the inside of the mount with a rubber dressing or dielectric grease, and reinstall it back into its bracket.

Next, familiarize yourself with one of the new coils. It doesn't matter which one; they are interchangeable.

The new coil has a long, square, center mounting post, running through the length of the coil--similar to the stock one. However, one side of the post sticks out longer, and has two bolt holes. See photo above. The new coil also has two, brass screws for mounting the input-wire terminals.

Open the small parts package that came with your new coils and take out two terminal-posts. Then mount them onto the coil, via the two, brass mounting screws.

As you tighten the screws, hold the terminal-posts so they are oriented out, sideways. See photo example below. This will make it easy to slide on the little input-wire connectors, once the coil is mounted. I oriented my upper terminal-post slightly up, and my lower terminal-post slightly down, which also made easier to slide on the input-wires.

Next attach the sparkplug wires to the coil. Find the two longest plug wires, put some dielectric grease on the metal terminals inside the 90* boot, and then push a 90* boot over each of the coil’s plug-wire nipples. Push them all the way on, until you can feel the terminal engage inside the coil.

Now lubricate the long-side of the coil's square mounting post with a little dielectric grease to make it easier to slide in. Then install the new coil. To do this, push the long side of the square mounting post into, and through, the rubber mount. Hold the rubber mount so it doesn’t get pulled through its bracket.

Keep wiggling and pushing the coil through the rubber mount until you can swing the coil into place. It's tight, but take your time. Then line up the bolt hole in the short end of the coil's square mounting post with the threaded bolt bracket on the bike's frame.

Screw in and tighten the small mounting bolt.

Push the input-wire connectors into the terminals on the coil. It makes no difference which wire goes to which terminal. However, if you are following the normal, stock convention, by wiring your left coil to the rear cylinder, be sure you've got the input-wire pair that includes a yellow wire.

Your left coil should now look like the photo below.

The right coil is mounted as a mirror image of the left one, so that the sparkplug nipples face rearward, just like the left ones.

Begin removing the right-side, stock coil by unplugging the two sparkplugs of the front cylinder.

Next, unplug the two little wires from the stock right coil. You don't have to keep track of which wire goes where--as long as you keep the wires for the right-side coil from ending up on the left coil.

Now unscrew the little bolt at the coil's rearward end.

The coil and plug-wire assembly can now be removed. Do this by swinging the bolt-end of the coil away from the bike enough to allow you to wiggle the other end rearward and out of its rubber mount.

Set the coil assembly aside.

Remove the rubber mount from the front bracket. Clean it. Then lubricate the inside of the mount with a rubber dressing or dielectric grease, and reinstall it back into its bracket.

Tip: You do not need to cut the rubber mount for the right-side coil.

Take out the other two terminal-posts from your small parts bag. Then mount them onto the coil, via the two, brass mounting screws.

As you tighten the screws, hold the terminal-posts so they are oriented out, sideways. Remember, you must orient the terminal-posts so that they point out, when the coil is mounted. See photo example below.

Next attach the remaining two sparkplug wires to the coil. Put some dielectric grease on the metal terminals inside the 90* boots, and then push a 90* boot over each of the coil’s plug-wire nipples. Push them on all the way, until you can feel the terminal snap or engage inside the coil.

Tip: I put the shortest wire on the rear-most nipple, and routed this wire to the right-side sparkplug, once the coil was mounted.

Now lubricate the short side of the coil's square mounting post with a little dielectric grease to make it easier slide in. Then install the new coil. To do this, push the short side of the square mounting post into the rubber mount. Wiggle and push the coil until you can swing it in place. It's tight, but take your time. Then line up the bolt hole in the long side of the square post with the threaded bolt bracket on the bike's frame.

Note: Yes, there are two bolt holes in the long end. The one furthest from the coil is not used for the Road Star.

Screw in and tighten the small mounting bolt. Since this coil is under some rearward tension from the rubber mount, be careful you don't cross-thread your bolt. Take your time getting the bolt cleanly started.

Push the input-wire connectors into the terminals on the coil. It makes no difference which wire goes to which terminal. However, if you are following the normal, stock convention, by wiring your right coil to the front cylinder, be sure you've got the input-wire pair that includes a white wire.

Your right coil should now look like the photo below.

Now screw on, and tighten the little top nipples for every sparkplug, if applicable for your type plug wires. See Parts List section above for details.

Put a little dielectric grease on the sparkplug tips.

Next you must use some trial fitting to find the best wire routing for your bike. Since throttle cable set-ups vary, crankcase ventilator set-ups differ, and fuel line routings vary, not all sparkplug wires will route the same.

I ran my rear cylinder wires from the left coil (photo above), along the frame backbone, and past the rear cylinder. Then I circled the wires back (in opposing directions) to each of the rear sparkplugs.

I ran my front, right sparkplug wire from the rear nipple of the right-side coil, circled the wire rearward-left, then ran it forward to the right-side sparkplug.

My front, left plug wire (photo above) was routed from the forward nipple of the right-side coil, around the outside of the rear nipple, then back and around to the front left-side sparkplug.

Once the wires are routed to your satisfaction, wire-tie them to the frame to pull them up off the rocker covers.

Tip: I only needed to use wire-ties for my rear cylinder, as my routing for the front cylinder automatically kept the wires up.

Now just reinstall the gas tank, and reconnect the battery. That's all there is to it.

There is very little that can go wrong with this installation. However, if upon starting your bike the engine sounds funny, rough, or stalls, turn it off immediately. Then check the following:

• Did you remember to screw on, and tighten the little sparkplug top nipples for every sparkplug, if applicable for your type plug wires? See Parts List section above.
• Are the sparkplug wires fully seated on the sparkplugs? If you used too much dielectric grease they might have unseated.
• Are the sparkplug wires fully seated into the coil nipples? If you used too much dielectric grease they might have unseated.
• Have you accidentally bent any of the sparkplug wire terminal-ends? If so, they may not be making good contact. Use a pair of needle-nose pliers to carefully bend the terminals back.
• Have you somehow gotten any of the little input-wires--two for each coil--disconnected or poorly seated?
• Have you accidentally broken or damaged any of the little input-wires or connectors?
• Have you securely tightened the brass screws for each of the input-wire posts?
• Have you somehow gotten any of the little input-wires mixed up? The coil for the rear cylinder (the left one, if you're following the normal, stock configuration) should have the wire-pair that includes a yellow wire. The coil for the front cylinder (the right one, if you're following the normal, stock configuration) should have the wire-pair that includes a white wire. Note: It doesn’t matter if the input-wires for each coil are reversed, as long as they are attached to the correct coil.
• Are both sparkplug wires for the rear cylinder attached to the left coil?
• Are both sparkplug wires for the front cylinder attached to the right-side coil?

If all the above checks out, but the engine still does not run smoothly, reinstall your stock coils and start the bike again. If the bike still does not run smoothly, you have likely damaged the connection within one or more of the little input-wire connectors. You must carefully check each one.

Start the bike again. If the bike runs smoothly with the stock coils, but not with the new ones (and all your connections are good), one or both of your new coils, or your sparkplug wires, may be defective. Contact your supplier.

Once everything is running well, you can relax, knowing your ignition system is running much more reliably.

Ride on.

Questions should be asked in our forum (Use discuss link below). The forum is very active and you stand a good chance of getting your questions answered there. If you would like to leave feedback for the author, or have additional information you think will benefit others, please use the comment section at the bottom of this page.

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DISCLAIMER: This information and procedure is provided as a courtesy and is for informational purposes only.  Neither the publishers nor the authors accept any responsibility for the accuracy, applicability, or suitability of this procedure.  You assume all risks associated with the use of this information.  NEITHER THE PUBLISHERs NOR THE AUTHORs SHALL IN ANY EVENT BE LIABLE FOR ANY DIRECT, INDIRECT, PUNITIVE, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, OF ANY NATURE ARISING OUT OF OR IN ANY WAY CONNECTED WITH THE USE OR MISUSE OF THIS INFORMATION OR LACK OF INFORMATION.  Any type of modification or service work on your motorcycle should always be performed by a professional mechanic. If performed incorrectly, this procedure may endanger the safety of you and others on your motorcycle and possibly invalidate your manufacturer’s warranty.

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