The terminals on the coils and also the connectors on the harness side can also corrode or oxidise, causing poor continuity to the coils. Check too, the LT wires/terminals at the PGM end.

The plug caps can also break down, and consider the fact that if they are original, they can be up to 18 years old now! Replace them with some decent silicone NGK caps.

Make sure the battery is 100%.

The spark can often appear weak, but may act very differently once the plug is back in the chamber and under compression. Testing for a spark with the plug out of the cylinder should be for that reason alone... testing for spark, not for quality of spark.
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Andy.
NSR-WORLD.COM

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