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Offline RickRR

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Spark-plug question
« on: February 14, 2010, 02:47:53 PM »
Hey guys,

I bought new plugs to put in my 78 750f, a ngk d8ea, took an old one out and its a ngk dr8es-l ?!?!?
what the difference between them and wich are the good ones ?

Thanks
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My heroes had the heart to live their lives out on a limb
And all I remember is thinking' I wanna be like them.

CB750F 1978

Offline dhall57

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  • The 70's! SOHC4 Honda's & Marcia Brady of course.
Re: Spark-plug question
« Reply #1 on: February 14, 2010, 03:00:34 PM »
DR8ESL are resistor plugs. I run the D8EA in my 76 CB750. I've been told that you shouldn't run resistor plugs in these bike.
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Offline tomsweb1

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Re: Spark-plug question
« Reply #2 on: February 14, 2010, 03:07:36 PM »
You don't need resistor plugs if you have resistor caps. Canadian bikes have resistor plugs, American bikes have resistor caps. Measure the ristance on your caps, and if it's minimal, stick with the es-l's... of course, if there's around 20,000 ohms... swap out for the regular ones you bought.
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Present: 1978 CB750A, 1978 CB400A, 1983 Nighthawk 550, 1984 CM250C

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Offline gane

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Re: Spark-plug question
« Reply #3 on: February 14, 2010, 03:20:11 PM »
Rick, NGK plugs are "readable" by their PN. D is thread size, 8 heat range,EA length of thread depth. the R, indicates resistor. SL is projected tip.  the differnce between D8ea & DR8esl is the 2nd is a resistor, extended tip. either will be fine for most applications. A purist might prefer the D8ea as the stock plug cap has resistor built in, the projected tips, offer a little better initial burn point, and being "swept" by gasses offer a slight cushion of heat range. hope this helps. G
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wdhewson

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Re: Spark-plug question
« Reply #4 on: February 14, 2010, 06:17:53 PM »
Has any body figured out the resistoe plug and cap business. 

Surely the biggest and most overwhelming resistance in this series circuit is the air gap between the plug's electrodes?
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