View Full Version : Spark plug question

02-24-2007, 11:15 PM
I have a '91 GSX 600F and I use a NGK DR8ES plug. I was told that you can go 1 plug hotter and it would help with performance. But my question is this true and which way would the number go ( up hotter or up lower spark performance. Also will this cause any damage to my moter?

02-25-2007, 12:22 AM
Lower numbers are hotter . But , no need . Won't help performance unless you have a problem , which the plugs will just mask until said problem gets worse . Running hotter plugs CAN cause you to run too hot , though . Not good .

The CyberPoet
02-25-2007, 12:42 AM
Spark plugs don't actually generate the heat; they simply help regulate the heat removal from the combustion chamber. The longer the insulator, the less heat is transferred from the combustion chamber to the head via the body of the spark plug. Lower numbers transfer less heat (leaving more behind, thus the common statement that they "run hotter").

A hotter plug is a stop-gap measure for an old bike that is burning too much oil or a poorly jetted bike, because it will let the spark plug get up to self-cleaning temps faster (thus reducing the odds of fouling) -- but by the same token, as MD said, it just masks the real problem. In a worst-case scenario, a low-enough numbered plug could reduce the heat removal from the chamber sufficiently to allow a lean fuel-air mixture to actually melt the aluminum of the piston heads (not a pretty site, to be sure).

As a final thought: as long as your spark plugs spark reliably when they are supposed to, without fouling, they've done their job, and no improvement can be made over that level of performance at the spark-plug end of the equation (a healthy spark is a healthy spark -- period).

=-= The CyberPoet