Do we really need resistor spark plugs?

My owners manual calls for NGK BPR8ES plugs, which are resistor plugs. Do we really need resistor plugs or can I run the NGK BP8ES, non-resistor plugs? I thought resistor plugs were to stop interference with radios, etc.

 

Man, Chacal is awesome! :lol:

Here's what he has to say about it:

http://xjbikes.com/Forums/viewtopic/t=44641.html (down towards the bottom of the page)

It is important to remember that you should strive to keep the ignition coil secondary circuit (plug wire, plug cap, and spark plug) total resistance as close as possible to original specifications, which are:

- 15K ohms per cylinder on all 1986 XJ700-X, XJ750-X, and XJ900 S/SH models.
- 10K ohms per cylinder on all XJ550, 1985 XJ700-X models, 1986 XJ700 non-X, XJ750RL, and XJ900 N/FN and F models.
- 5K ohms per cylinder on all XJ650, 1985 XJ700 non-X, all 1981-83 XJ750 models, XJ750-D, XJ900RK and RL models, and XJ1100 models.

For people who wish to rebuild their otherwise usable original Tokia Denso plug caps, we offer replacement resistors in either the 0K, 5K, or 10K versions, or a non-resistive (0 ohms) replacement rod. Owners who wish to use non-stock spark plugs (such as the popular NGK Iridium plugs or any other replacement plugs) will need to make the appropriate reduction in the secondary circuit total resistive load, which is most easily achieved by reducing the resistance of the plug caps by 5K ohms from their stock specifications.

NOTE: there may be some benefit to reducing your plug cap resistance by 5K from stock values, and increasing the spark plug resistance by 5K from stock, since spark plugs normally need to be changed every 7,500 miles or so, and when changing the spark plugs, you are also automatically "re-setting" its resistance value. Otherwise, in most stock configurations, your 0K (non-resistive) plugs gets changed frequently, but your plug caps are retained, even though their resistance ratings are deteriorating over time. By "transferring" the resistive load from the very infrequently replaced plug caps to the rather regularly replaced spark plugs, you then get to take advantage of the regular replacement cycle that naturally occurs with spark plug changes.