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Discussion Starter · #1 ·
Morning all

I have been giving my GL1200 a check over and decided to check the coils for resistance. Primary resistance is as per specs as is the resistance from spark plug caps to coils. By this I mean checking resistance between plug wires for cylinders 1&2 and 3&4

Now here is the confusing part. The secondary resistance when plug wires have been unscrewed from both coils is under spec at 14K ohms when the manual I have says it should be between 16K –to over 20K Ohms.

So now I am thinking should this not be effecting the bike and how come the resistance at the spark plugs are within spec indicating the coils are working but when the plug wires are unscrewed from coils the cois give a under spec reading.

Any ideas?
 

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The spec is for wire to wire.
Each of the plug wires has a resistor installed in the spark plug cap. Look into the bottom of the caps. You'll see a brass fitting with a screw slot. Unscrew it but be ready to catch the resistor and spring. Once you have the resistors out you should clean them with crocus cloth or electrical cleaner then reassemble them.
 

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Discussion Starter · #3 ·
The spec is for wire to wire.
Each of the plug wires has a resistor installed in the spark plug cap. Look into the bottom of the caps. You'll see a brass fitting with a screw slot. Unscrew it but be ready to catch the resistor and spring. Once you have the resistors out you should clean them with crocus cloth or electrical cleaner then reassemble them.
Ahh I see. So there is no spec so to speak to test the coil directly by putting a meter on its terminals and no wires involved
 

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If it runs good the coils are OK, those coils are so close to the minimum requirement that any weakness in them will show up in performance problems.
 

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Discussion Starter · #5 ·
If it runs good the coils are OK, those coils are so close to the minimum requirement that any weakness in them will show up in performance problems.

Thanks thats good to know. Just in case they get any worse what symptoms would show?
 

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Thanks thats good to know. Just in case they get any worse what symptoms would show?

Missing or cutting out at higher RPMs or under load.
 

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wildfire,

I am doing the same to my 84 Gl1200. Manual has testing leads 1-2,3-4 with caps resistance should be around 24k. Without the caps on the manual shows wire to wire should show about 19k.

Testing both of my coils wire to wire resistance is showing 14.25k.
Looking on Randaks site the coil resistance is stated to be about 14k per coil wire to wire. So it seems the coil resistance at 14k is good.

I am replaceing the ignition wire and caps (XD05FP) on the wing, the wires were way too stiff.
 

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Most good independent m/c shops carry new NGK spark plug caps and bulk wire(6' = (4)-18") for @$30 . Start there if they are original wires and caps. That and new NGK spark plugs.
 
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