Spark plugs for motorbikes (made by NGK - Japan)

With standard central copper, platinum, or iridium electrode (new).

Highly tuned engines need colder spark plugs (where NGK spark plugs are used, install plugs with a higher heat range index number than the stock units). If you do not know the correct heat range, it's best to install a fairly cool plug. If the spark plug tends to foul during operation and thus causes misfiring, change to a spark plug with a slightly lower index number. For obvious safety reasons, the rule of thumb is to use the coldest plug that the engine can tolerate without leading to fouling. 
 

Standard NGK spark plugs
 

Iridium NGK spark plugs

Platinum NGK spark plugs