Plug wire/connector separation...

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FJR Supporter
Apr 11, 2023
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Greenville, NC
Finally getting around to checking valve clearances ('07 with 55K and I think I might be the first one in here). And I and did this.

The last type of vehicle I did my own work on (89 Mazda pickup) I knew how to fix this.

On this beast I'm not so sure. I don't even know where the other end of this thing starts.

What am I in for here? Any repair advice?


Edit: To attach a picture of the wire end. It's green. Hard to tell if it's corroded copper or some other verdigris.


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Corroded copper. Trim a minimal amount off the end of the wire (there isn't much spare length so maybe a 1/4" or so).
Inside the top of the plug boot, there is sort of a skinny spiral spike (I assume it didn't break off). Essentially, you screw the spike into the wire by twisting the boot.

Before reinstalling the boot/wire onto the plug, smear a THIN coating of silicone grease on the rubber that contacts the valve cover and clean the rim of the opening in the valve cover. Makes future removal easier. A thin smear at the end of the boot where the boot contacts the plug insulator helps as well. The silicone dielectric grease is also helpful for the headlight boots...
What RossKean said, plus take a good look inside the boot at the "skinny spiral spike" and make sure its not corroded. I recently trimmed all my wires and had to replace a boot ....and long story short, one of the boots I bought off ebay was corroded to the point of the "spiral spike" inside the boot was no longer there. Hope that's not the case for you.
Thanks guys! The advice here is pure gold.

It's hard to see down into the top of the boot but it looks more like a post and less like a spiral/screw. May be best to replace just to be sure. It didn't come off from pulling - although some grease would have made things easier. It came apart when pushing it under the cooling system plumbing - I bent it and it came apart.

When removing the cooling system plumbing I noted much corrosion. It was so bad that I think one of the o-rings had disintegrated. Only the right side o-ring was intact.

I read somewhere there should be three o-rings, but I've only encountered these two so far - and I don't see where a third will come from.

Maybe this will become obvious when I finally pull the valve cover?

Final question (and again TIA): I'm planning on deleting the AIC? system - all the extraneous emissions plumbing. I have a set of plates and see where they go. What I'm not sure of is what to do with the single electrical connection. Do I just unplug and remove the device on the hanger? I'll add a picture to illustrate. If I just unplug it will the sensor system detect a problem?


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Gen I has a third o-ring that should be replaced at the thermostat. Gen II has just the two for the coolant pipe.
Used coils (with attached wires) plus plug boots are often found on eBay. Be vary careful about wire routing around the coolant pipe. Yamaha should have spent an extra nickel to give us another inch of wire!

No issues with Gen II for the AIS. Gen III+ will complain.
Your accidental separation of the plug cap from the wire is a golden opportunity to check the resistance of the plug cap.
Using a VOM set to the Ohms resistance scale, measure the resistance from the spiral spike end to the inside connector that plugs onto the spark plug. Should find approximately 10,000 ohms resistance, or thereabouts.
If significantly different, the cap can be disassembled by using a screwdriver inside the end that plugs onto the spark plug to unscrew the connector.
Inside the cap will be a spring and a resistor slug. Clean up all the parts, including inside the cap and reassemble.
Re-check for total resistance and if approximately 10,000 ohms, good to go.
Push / screw the cap back onto the spark plug wire.

If you find the first one out of spec., might be a good idea to check the others, too.

Thanks, Dan! I did figure-out how to unscrew it and release the spring and (what I now know is a) resistor plug. The plug did have some oxidation that came right off.

I have it all back together now and it's working, otherwise I'd do the test you recommend. I took off about 0.25" from the wire and did my best to screw it back on and it seems to have worked.

I really appreciate the advice here!