High-G FJR Junkie!
Join Date: Oct 2005
Location: Australia No fixed address
The one thing that nobody seems to take notice of in the vibration and throttle body balance discussions, is spark plugs. I've always found that old, worn, spark plugs are a significant contributer to vibration. As a general rule, when using standard plugs, you should change them every 10K Km. With Iridium plugs, I change them at 20K Km, and I always notice a reduction in vibration with fresh plugs. When I am going to carry out a throttle body balance, step one is to replace the plugs.
I know that a lot of people run their plugs 5 to 10 times longer than I do, and the bikes will run OK for that distance, but the penalty is vibration, trust me.
The reason is that, when an ignition system generates a pulse of high voltage to spark a plug, the voltage is not an instantaneous thing, it takes time to rise to the level at which it will arc across the plug gap. When the plug wears, the voltage, and therefore time, at which the arc occurs is not constant, it will change at every cycle. Thus, the ignition timing is constantly changing on all cylinders, all the time, and the result is vibration.
FJR Models owned from new, 2001, 2003, 2006, 2009, 2011, 2014.