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Steve
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I just bought 4 NKG DP8ea9 plugs........ Can these be used, or should I go and repalce them for DP7ea9 as per the manual. ?
 

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You could run them, but if you haven't used them see if you can swap them for the 7's. If the plug is too cold, there will be deposits on the nose of the plug. What did your old set look like? If you don't have any oil or carbon fowling you should be ok with the colder plugs.
 

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I would go with Iridium #7803 DPR7EIX-9 first. If not go with DP7EA-9. Advance Auto had Iridiums at $6.99 each
 

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Linkmeister Supreme
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I would go with Iridium #7803 DPR7EIX-9 first. If not go with DP7EA-9. Advance Auto had Iridiums at $6.99 each
X2^^^^^^^^^
Get the NGK Iridium DPR7EIX-9 plugs.
They will probably outlive the bike!!
 

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1986 VN750
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X2^^^^^^^^^
Get the NGK Iridium DPR7EIX-9 plugs.
They will probably outlive the bike!!
Seconded.

They woke my bike up! Old plugs couldn't even get her started, and she roars to life first push of the starter now.
 

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Per/on topic-off topic.......has anyone running too rich ever tried running "6s" instead of the 7's ?...after my Harley muffs, Im running a hair rich. Tried the gap-closing trick to get a hotter spark, but they tended to just foul then. Suppose the worst that could happen is melting holes in the top end, eh ?
 

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Per/on topic-off topic.......has anyone running too rich ever tried running "6s" instead of the 7's ?...after my Harley muffs, Im running a hair rich. Tried the gap-closing trick to get a hotter spark, but they tended to just foul then. Suppose the worst that could happen is melting holes in the top end, eh ?
If you are running rich, you need to fix it by adjusting the carbs, not the plugs.
 

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Per/on topic-off topic.......has anyone running too rich ever tried running "6s" instead of the 7's ?...after my Harley muffs, Im running a hair rich. Tried the gap-closing trick to get a hotter spark, but they tended to just foul then. Suppose the worst that could happen is melting holes in the top end, eh ?
A slightly rich mixture tends to increase power; however, it also increases fuel consumption and exhaust emissions. An overly rich mixture, 8:1, will reduce engine power, foul spark plugs, and cause incomplete burning (black smoke at engine exhaust). But really no damage to the engine unlike a really lean mixture, 20:1, would cause due to the high heat. Ideal mixture is 15:1.

If you really wanted to, you could take it to a shop and have them test the exhaust gases.
 

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take it to a shop and have them test the exhaust gases
NEVAH !!!!!...I only hit the shops for parts and inspections, lol...I'll just get a set of Irridium 7's...carbs seem to be where they need to be...just looked like a weak spark when I tested (visual spark test).
Have no popping/backfiring and MPG is about 58 if I ride nice and in the flats.....I mighta worn out the old plugs from all the adjustments/mods ive done in the last few months.
I just asked about the 6's because thats what we did when I was racing motocross with my Bultaco and it ran rich (went hotter)...that was a 2 stroke though with premix...
 

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NGK Iridium DPR7EIX-9 plugs= These are the plugs I got today, my plug wires will not fit them. Do I need to get special plug wires to go with the larger tipped end, and which ones do I get? Thanks.
 

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A slightly rich mixture tends to increase power; however, it also increases fuel consumption and exhaust emissions. An overly rich mixture, 8:1, will reduce engine power, foul spark plugs, and cause incomplete burning (black smoke at engine exhaust). But really no damage to the engine unlike a really lean mixture, 20:1, would cause due to the high heat. Ideal mixture is 15:1.

If you really wanted to, you could take it to a shop and have them test the exhaust gases.
Your numbers are off quite a bit.

Theoretical ideal mixture is 14.7:1 with gasoline. Max power is generally around 12.8-13. 11.0 is pig rich, and 15 is dangerously lean. These are Wide Open Throttle figures. Cruise/part throttle can be significantly leaner than what the engine needs at full throttle.

That being said... I don't know about the Vulcan, but more often than not, bikes from the last 15 years or so come jetted very lean from the factory for emissions. They can be right on the edge of safety. Adding free flowing air filters and exhausts lean them out even further. These modifications generally require re-jetting to do them right.

My Vulcan is just a cruiser, and still has the stock air filters and exhaust... and the carbs on these bikes look to be a PITA to remove, so I'm just fine leaving it stock. However, all my dirt bikes were very lean from the factory, and required significant re-jetting with the addition of free flowing air filters and exhausts.

The mustang is a different animal. It's carbed, but I use a combination of a wideband oxygen meter and the drag strip to dial in its carburetor. The wideband is best for adjusting drive-ability and getting the main jetting in the ball park, but the strip is best for getting the WOT jetting dialed in just right. (jet for highest mph)

Good Luck!
 

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NGK Iridium DPR7EIX-9 plugs= These are the plugs I got today, my plug wires will not fit them. Do I need to get special plug wires to go with the larger tipped end, and which ones do I get? Thanks.
You have the automotive type wires as I have. Just go to an auto repair shop you know and ask em for 4 old plugs with screw top ends (AC plugs are fat, but permanently attached)...Champion ends fit nicely on the NGKs. Im sure they'll give ya the old ones for nuthin.
Or....you can get 4 stock NGK ends, 2 short, 2 deep, at a dealer for about $4 each. They will attach to your existing wires.
 

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Related question....My '85 700 stock wire ends have what looks to be a fuse inside and spring loaded (Im guessing its a resistor for RF)...yes, I actually disassembled a stock end and replaced the wire clip that clamps the top of the plug...anyone remove em (resistors) and run without. I was never into resistor plugs and such and am wary of things like that. I need all the spark I can get.
 

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NGK Iridium DPR7EIX-9 plugs= These are the plugs I got today, my plug wires will not fit them. Do I need to get special plug wires to go with the larger tipped end, and which ones do I get? Thanks.
No, The larger tip end unscrews from the plug. Just take it off and the boots will fit fine. :smiley_th
 

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...ahhhh....my bad...I didnt know the Iridiums came with screw tops....I ASSumed they were like the OEMs....
 
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