You should put a new one in and ride it to test the jetting.
When you do a wot high speed throttle chop, check the location of the heat mark on the ground strap.
Go somewhere where you can hold it at wot in 6th gear preferably under light load for 40 to 60 seconds.
Get it warmed up to temp. Put a brand new plug in it.
Go right to wot, full speed, 60 seconds, pull the clutch in and let off the throttle and hit the kill switch all at the same time. Take the plug out and put the old one back in, What you'll be looking for is the hot spot on the ground strap and the color ring around the base of the center electrode (way up inside the plug).
The color of the ring will tell you if it's rich or lean, if it's excessively one or the other you might want to get the main jet right before shooting for heat range.
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