Sparkplug appetite

[ventoman]

My vento has a appetite for sparkplugs it seems. I have to replace them about every 500 miles. It has always been this way. I use nkg plugs. I have tried different heat ranges over time. The hot brh7 plugs last the least the brh8 last the longest. I tried autolite brands with similar results. The plugs when pulled look ok not burned with tan coloring. Tuning is good and the scooter runs well until the plug goes bad and the it starts missing at high speed operation. Why does it go thru plugs so fast? I do not know. I have ordered a iridum plug to see if that will last longer. If that don't work I will try a different oil instead of the vavoline I have been using.