Got the spark plugs removed. All looked ok - except the plug from cylinder #4 - which had a
bridged gap! An extremely thin filament between the ground electrode and the center electrode! :omg:
So I gapped the new NGK CR9EIA-9 in accordance with specifications (thanks for the information!) and installed these. I routinely put anti-seize compound on spark plug threads whenever changing these and grease the cap for easy removal next time. The plugs removed were the original ones and noticed these were not installed tight enough - these were actually almost loose. :omg:
I buttoned everything back up and started it. The auto fast idle sounded ok, and after a minute or 2 the idle speed dropped back to around 1100 rpm and still sounded fine. So it was the plug with the bridged gap that was causing it to run rough! I went for a ride and filled up the tank.
Now runs as smooth and fast as it ever did!
Tools and other considerations -
* removal of fasteners at the top of the right hand side of the fairing to make removing the air box easier.
* clean lint-free rag to cover the throttle bodies to prevent dirt/dust/whatever else from falling into these.
* compressed air to clear the grit from the spark plug recesses before spark plug removal - wear safety glasses.
* it's a long reach to the spark plugs so I used a length of tubing attached to the spark plug when threading these in - prevents
disastrous cross-threading.
* anti-seize compound applied to the new spark plug threads for proper care of the aluminum threads in the cylinder head and ease of removal next time.
* multi-purpose grease for the spark plug caps for ease of removal next time.
* magnet to extract loosened spark plugs (my damn spark plug socket wouldn't grip the loosened spark plug).
* multi tester, diagnostic check of the ignition coils resistances, all were within spec. (1 ohm primary and 10k ohm secondary).
* tunes in the garage. :coolcool:
Note: recommended spark plug replacement interval is 7500 miles/12 months.