What Spark Plug for Shadow 500 - Honda Shadow Forums : Shadow Motorcycle Forum
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post #1 of 11 (permalink) Old 08-05-2012, 06:54 PM Thread Starter
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What Spark Plug for Shadow 500

I know this may be a dumb question, but I can't find an answer online for the life of me...

So, my bike has been running way rich... And of course, the plugs are pretty well fouled out. Im working on getting the carb functioning right, but I figured Id get it a new set of spark plugs while I was at it.

Well, what am I looking for here? I understand that these bikes use NGK plugs, but Im just looking for a number.

What do you run? Thanks in advance.
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post #2 of 11 (permalink) Old 08-05-2012, 07:30 PM
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Go on the ngk site it should tell what plugs are best
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post #3 of 11 (permalink) Old 08-05-2012, 07:51 PM Thread Starter
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Shoot, why didn't I think of that?

Anyway, just incase anyone stumbles across this thread in the future, a VT500C takes:

DPR8EA-9

Stock No. 4929

Gap: .035"

Thanks
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post #4 of 11 (permalink) Old 08-06-2012, 02:43 AM
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could also use DPR7EA-9 or DPR7EA-9 depending on climate and how the bike is ridden. also found in the owners manual Stickied on this site.

84 VT500


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post #5 of 11 (permalink) Old 08-06-2012, 02:56 AM
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Nice! I just had a similar question engine rebuild and more...

The NGK DPR7EA-9 are for cold climates
the DPR8EA-9 are the stock spec
the DPR9EA-9 are for "performance" bikes

I'm also curious what these temp ratings mean. I guess I'm more interested in the fundamental "why", that is to say what is the difference between these plugs that makes them suited for these different environments? Sorry if I'm hijacking your thread, just tell me to shut up.

But to answer your question, the DPR8EA-9 is the spec plug. But as rosco said, it depends on climate and riding environment. How? IDK, but that's what I'm after.


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post #6 of 11 (permalink) Old 08-07-2012, 02:20 AM
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Quote:
Originally Posted by mattyo View Post
Nice! I just had a similar question engine rebuild and more...

The NGK DPR7EA-9 are for cold climates
the DPR8EA-9 are the stock spec
the DPR9EA-9 are for "performance" bikes

I'm also curious what these temp ratings mean. I guess I'm more interested in the fundamental "why", that is to say what is the difference between these plugs that makes them suited for these different environments? Sorry if I'm hijacking your thread, just tell me to shut up.

But to answer your question, the DPR8EA-9 is the spec plug. But as rosco said, it depends on climate and riding environment. How? IDK, but that's what I'm after.
the 7,8,and 9 are the temperature ratings. On the ngk the plugs are on a scale of 2 to 13, 2 being the hottest and 13 the coldest. The insulator of a spark plug is a very poor conductor of heat, so it uses the metal of the spark plug to dissipate the heat. On the hotter spark plugs the there is less of the insulator tip touching the metal of the spark plug. With less surface contact there is less transference of heat thus creating a "hotter" spark plug. A colder spark plug is just the opposite there is more surface contact in between the insulator tip and the metal of the spark plug allowing more heat to escape.


Now on are engines the the different heat ranges called for in different climates and driving conditions are easy to figure out. If you live in an average climate, and do shorter stop and go city type driving you want to use a the DPR8EA-9. in a colder climate and sometime an older engine you want to use the DPR7EA-9 this helps keep everything running around optimal temperature and performance. On older engines, running rich or leaky oil rings, the hotter temperature helps to keep the spark plug clean instead of fouling it out, not the proper fix obviously but is one solution. In a hotter climate or on a motorcycle driving at higher RPMs for longer period of times, high performance or highway driving, you want to use the DPR9EA-9, what this will do is help from heating the cylinder up to much and causing engine knocking or pinging, preignition where the fuel air mixture ignites before the spark plug fires witch can cause the temperature to raise significantly in the cylinder causing burnt valves or even melt parts.

hope this helps more than confuses you.

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post #7 of 11 (permalink) Old 08-07-2012, 02:39 AM
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Rosco, THanks! I learned something new
That's a great explanation
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post #8 of 11 (permalink) Old 08-07-2012, 02:52 AM
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Excellent description rosco! That helps me out a lot! I had it all backwards. I thought a cold plug meant the plug ran colder, ie dissipated more heat. I guess at some point it comes down to semantics, but you definitely helped clarify the situation for me. Thanks!

So just to make I sure I understand this. A "cold" plug actually runs hotter. The "cold" refers to the engine/climate temp which means you want a plug that runs a bit hotter?


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Last edited by mattyo; 08-07-2012 at 02:59 AM.
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post #9 of 11 (permalink) Old 08-07-2012, 04:15 AM
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Quote:
Originally Posted by mattyo View Post
Excellent description rosco! That helps me out a lot! I had it all backwards. I thought a cold plug meant the plug ran colder, ie dissipated more heat. I guess at some point it comes down to semantics, but you definitely helped clarify the situation for me. Thanks!

So just to make I sure I understand this. A "cold" plug actually runs hotter. The "cold" refers to the engine/climate temp which means you want a plug that runs a bit hotter?
you hit that backwards, a cold spark plug does run colder and a hot spark plug run hotter. in cold climate use hit spark plug and in hit use cold.

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post #10 of 11 (permalink) Old 08-07-2012, 12:36 PM
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Originally Posted by roscoenr View Post
you hit that backwards, a cold spark plug does run colder and a hot spark plug run hotter. in cold climate use hit spark plug and in hit use cold.

Sent from my PG86100 using Motorcycle.com App
LOL! I keep confusing myself. All is clear now. Thanks again.


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