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Discussion Starter #1
I changed my plugs over to the NGK Iridium plugs the other day and that first day my bike ran awesome. But in the days since, my gas mileage dropped (I'd heard it should increase if anything), my bike takes a long time to start, and it doesn't seem to have as much power. I checked the plugs and wires and they all seemed tight, so I pulled all the plugs to check them and they look a little white, perhaps from running a little lean? Any thoughts are welcome!
 

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Love My Baby
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check the spark plug gap. did you do ANYTHING else beside change the plugs?
 

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Premium Member
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Don't know what year your bike is so I'm shooting in the dark. Was your bike running great before the plug swap? If so, then I'd look at your plug wires and caps. More than likely something got damaged in the swap or was already cracked or worn out and pulling them off and putting them back on temporarily worked but now the problem is worse. If they're old it would be time to replace them anyway.
 

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Discussion Starter #4
Ok, its an '03 and all I touched was the plugs. How do I check the gap and what would I be looking for in the wires?
 

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Old Truck Junkie
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4,133 Posts
Do you still have the old plugs. If so try going back to them. From time to time you can get a bad set of plugs.
 

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Linkmeister Supreme
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Ok, its an '03 and all I touched was the plugs. How do I check the gap and what would I be looking for in the wires?
You will need a wire type spark plug feeler gauge to check the gap. If the plugs don`t have multiple electrodes on the circumference of the base, but ony 1 L shaped electrode close to the center electrode, you can also use a coin shaped, ramp type feeler gauge. (Bottom one in link below.)

If you have a Clymers manual there are pictures in chapter 3 on page 97, that show you how to use the gauge.

Table 6 at the end of Chapter 3 gives the gap as 0.8-0.9mm, or (0.030 -0.040 inches, read as 30 to 40 thousandths of an inch).

Here is a link so you can see what you need. (The flat feeler gauges are not used for plugs, but for other jobs.) http://www.mytoolstore.com/kd/kdfeel02.html

Try checking your plugs and wires for spark by grounding the plug base against the engine while pressing the starter button with the ignition turned on. Any that don`t give a bright spark, exchange the new plug for one just taken out and try again. If you still don`t get a bright spark, you may have a bad wire or connector in the boot.

Disconnect the plug wire from the ignitor and do a continuity check with an ohm meter. If you get infinate resistance the wire is broken. I can`t find any referece to what the resistance should be for copper core wires that the vn has. (Carbon core wires on my `92 Olds should be 5000 to 7000 ohms per foot, I believe.) If you get any resistance reading, other than infinite, you know the wire is not broken.

Anyone else know what resistance reading we should get on the plug wires?

Good luck.
 

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Discussion Starter #7
No, i threw the old plugs away. I'll check the wires tomorrow and then post an update.

Thanks!
 

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Discussion Starter #8
I never got a chance to check the wires, but decided to run some seafoam through the tank in the meantime. I figured it couldn't hurt and the bike is running much smoother now. As far as the starting goes, it has a hard time starting, and sometimes won't even begin to turn over unless I'm in neutral. If I put the bike in neutral it fires first try almost every time. My guess is maybe the sensor in the clutch is beginning to go. I was wondering if that sounded right and if so, what's the best way to check it?
 

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Benjammin'
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421 Posts
Glad to hear there is some improvement in the way the bike is running. As far as gapping the iridium plugs- be very careful. The iridium metal that coats the center electrode is very hard, but also very brittle. A feeler gauge can chip the metal.
 
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