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This How-to outlines the steps required to install individual coils on your spark plugs on an fzr 600. This should work on any bike that came with the same TCI unit as the fzr600, just double check the wire colors.

Parts required:

The coils I used were Denso part number 129700-3881. This is available off the following bikes:

  1. 1999-2000 Honda CBR600F4
  1. 2000-2003 Honda CBR929RR
  1. 2001-2006 Honda CBR600F4

There may be more but basically you are looking for something like this:-

Those setups come up on ebay all the time and I scored a set of F4 coils w/ harness for about $20+shipping.

A few more notes about the parts, I tested the primary resistance of the stock coils to be about 4.2ohms. The CBR coils come in at 3.0-3.3 ohms. Ideally you would want half of the resistance of the single stock coil, since you are replacing it with two coils. So, if you're feeling ambitious and want to try another set of COP coils, make sure the primary resistance is roughly half of one of the stock coils. Other parts needed: solder soldering iron small heat shrink tubing extra wire (18ga is fine)


Remove seats, tank cover, fairings, radiator (no need to disconnect just get it out of the way), airbox…


Remove the stock coils and leads.

Ok, now before you throw those boat anchors that Yamaha used as coils into the trash, clip off the connectors and remove the bracket. You will need these to make your custom coil harness.

Grab the Honda coil harness and start by ripping apart all the tape and sheathing that comes in it. You're pretty much only interested in the plugs that go to the C-O-P sticks, but leave as much wire as you can on each one.

Making the harness

The next steps walk you through how to create a harness that will do this:

Lay out the plugs for the coils that will go between cylinders 1 and 4 and cut one of the black wires to length so that it will join up with one of the non-black wires on the other connector. In other words, you are joining the negative side of one coil to the positive side of the other coil. Solder and heatshrink the connection between those two wires.

Now take that assembly and measure it up so you know how much wire you need to connect the remaining two wires to the stock coil connection. This is where I had to use spare wire to extend the connection. Take the remaining black wire and connect it to the Orange wire on the (orange) harness you clipped off the stock coils. Connecting the coils in this manner makes it so that the ground is switched on the coils.

Here is a picture of the connection between two of the coils (positive side to negative side):

Take the remaining non-black wire and solder it to the red with white stripe wire on the (orange) harness. Don't forget to put the heat shrink on before you solder the wires!

Now you should have something that looks like this:

Repeat what you just did but this time for cylinders 2 and 3. The only difference will be less wire between the coil connectors (since they are physically closer), and instead of connecting to an orange wire, you will now be connecting the black wire to a gray wire.

When you finish that you should have something that looks like this:

Note that the yellow harness plug goes to cylinders 1 and 4 while the white harness plug goes to cylinders 2 and 3.

Installing the coils Make sure you are using the type of spark plugs that have removable tips. I found that screwing the coils on seems to hold them better. The ends of the two inside coils will be leaning up against the fan supports. I rotated the fan manually while moving the coil around trying to simulate a driving condition, and I couldn't get the coil to go into the fan. Your bike may be slightly different, so I highly recommend that you check this before continuing.

This picture illustrates what I'm talking about with the fan:

Plug in your harness to the coils and feed it up through the splash guard. Connect the harness to the corresponding connectors where the old coils used to connect.

Now you can do a test fire! It should work. If it doesn't check your solder joints on your harness, and if that fails you might have received bad coils. Check the primary resistance and make sure it is within 3.0-3.3 ohms, or around there.

Install the old coil bracket so the splash guard doesn't flap around and zip tie any excess wire. Make sure the wire doesn't get caught in the fan somehow.

Here is a picture of the old coil mounting points.

And this is how the coils look installed:

Put everything back together and go for a ride!

If it feels the same as it did before, then the mod worked! ClapHands

I did this mod because I'm hoping to cure a rain cut-out problem. I have not yet driven in the rain with this mod yet, but in the dry it rides exactly as it did before.


I can not say what this mod will do to the transistors inside the TCI box in the long run. This mod could possibly reduce the life of the transistors. MOD AT YOUR OWN RISK!

coil_over_plugs_mod.txt · Last modified: 2020/10/19 11:51 by