Below you will find charts with plug cross references by brand.
Different brands work better on different types of engines, so generally you want to use the same brand and part number plug recommended by the manufacturer. There are some plugs that are very specific to a type of engine. You should verify the plug works with your application.
NGK NUMBERING SYSTEM:
If you are using the plug recommended by the manufacturer, 99% will be properly gapped out of the box. But you should always check the gap to ensure it meets the mfg specs. (EXCEPT Iridium plugs!)
Part of the spark plug's job is to reduce heat in the combustion chamber by channeling heat through the insulator material and metal housing, and into the cylinder head where the cooling system can handle it. So using too hot a plug can lead to overheating, power loss, pre-ignition, detonation and engine damage. Plugs that are too cold can foul out, misfire and poor performance.
- runs at higher temperature
- more prone to pre-ignition
- less heat is absorbed by the plug and passed to the cooling system
- longer insulator
- runs at a lower temperature
- more prone to fouling
- more heat absorbed and passed to cooling system
- shorter insulator
Its always better to fix the problem than to try and patch it with plug changes. But a colder plug can be used on an engine that is running hot and a hotter plug for engines running cold.
For NGK plugs a p/n lower than the base is a hotter plug, and a p/n higher than the base is a colder plug. So for DPR6, DPR7 is colder, DPR5 is hotter. Always check with the plug manufacturer to ensure the plug you choose is compatible with your bike. Racing plugs have a different numbering scheme.
There are several different styles of plug caps. You should try to use a cap that best matches the angle between the plug wire and the plug itself. Avoid the decorative or sparking caps. These do lower the power to the plug.
If you are interested in the process of reading plugs... have a look at this page.
Iridium is a precious metal that is 6 times harder and 8 times stronger than platinum, it has a 1,200 degree (F) higher melting point than platinum and conducts electricity better. This makes it possible to create the finest wire center electrode ever. Prior till now, platinum had been favored for long life or performance spark plugs due to its high melting point. Also, the technology did not exist to machine and bond iridium on a spark plug electrode (at least in a cost effective manner).
First, if you decide to use IR plugs, use high performance wires. Actually the whole ignition system should be high performance.
IR plugs are longer lasting (40,000-60,000 mile claims); they
IR plug brands:
Manufacturers' indicate you should NOT gap a new IR plug.