Sparkplug Cap Resistor?


44 replies to this topic
  • Rman of 237

Posted August 23, 2007 - 09:31 PM

#1

What's the purpose of the resistor in the sparkplug cap? It can't be good. Does it delay the spark somehow as part of the smog crap?:lame: I know some folks that removed it and cut a #8 or #6 bolt shank to use for a conductor. I bought my 650 second hand so I checked to see if it still has the resistor and it does.

R.....

  • crmc33

Posted August 24, 2007 - 01:13 AM

#2

to pevent radio interference

  • Rockjockey

Posted August 24, 2007 - 03:24 AM

#3

To keep you guessing when it goes out.

  • martinfan30

Posted August 24, 2007 - 07:38 AM

#4

To keep you guessing when it goes out.


this is more like it! i pulled a bonehead move when i pulled mine out and didnt put something in to complete the gap. then i couldnt figure out why it wouldnt start!!!!:bonk: :bonk: :bonk: :bonk: :bonk: :bonk:

  • XR650L_Dave

Posted August 24, 2007 - 07:49 AM

#5

And other than the fact that it could fail, there is no downside to leaving it in.

(But that kinda says it all, doesn't it?)


Dave

  • Rman of 237

Posted August 24, 2007 - 08:05 AM

#6

to pevent radio interference

Radio interference? Well wouldn't that make it a condenser? It looks like a resistor. I really don't want the damn thing in there if it's just something else that can break.:banghead: Does this thing impede performance? If so how and why?:excuseme:

  • martinfan30

Posted August 24, 2007 - 08:09 AM

#7

Radio interference? Well wouldn't that make it a condenser? It looks like a resistor. I really don't want the damn thing in there if it's just something else that can break.:banghead: Does this thing impede performance? If so how and why?:excuseme:


pretty sure its a resistor, just like resistor plug wires on a car. dont think it really impedes performance, just ease's your mind on 1 less thing to fail.

  • beezerjoe

Posted August 24, 2007 - 08:19 PM

#8

From what my honda dealer told me it's there to help give a hotter spark. I took mine out and it doesn't seem to really have made a difference. It's still a bit of a pain to start when cold but runs and starts good when warmed up. Seems like a useless part if you ask me.

  • HeadTrauma

Posted August 24, 2007 - 11:12 PM

#9

It's ironic that the Honda power equipment engines have the same thing. However, I was just reading on a kart racing forum that it can slowly zap the secondary circuit in the coil. I know, different ignition systems and applications, but something to consider.

Besides, a hotter spark isn't necessary unless it's getting blown out from *extremely* dense mixtures. It usually takes forced induction to do that on a healthy ignition system.

  • martinfan30

Posted August 25, 2007 - 10:39 PM

#10

From what my honda dealer told me it's there to help give a hotter spark. I took mine out and it doesn't seem to really have made a difference. It's still a bit of a pain to start when cold but runs and starts good when warmed up. Seems like a useless part if you ask me.


i dont see how this is even possible. a resistor will restrict current flow. not only that but a spark plug doesnt generate heat more or less by the heat range, that is a measure of how quickly the plug transfers heat.

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  • Natnewt

Posted March 01, 2009 - 08:58 PM

#11

the cap looks to be all one piece where is the resistor in it and do i have to cut it open to find out?

  • martinfan30

Posted March 01, 2009 - 09:14 PM

#12

the cap looks to be all one piece where is the resistor in it and do i have to cut it open to find out?


Look inside the boot. There is a slot screw that holds it in place.

  • Maxzillian

Posted March 01, 2009 - 10:03 PM

#13

From the quick reading I've done before bed, it appears that the resistor is good for increasing the duration of the spark. This is because the coil produces a certain amount of energy, resistor or not. With the resistor in place, this discharge of energy is slowed down, allowing for a longer spark duration. However, this is at the cost of a slightly weaker spark. The reduction in current also greatly reduces electrical interference.

  • Natnewt

Posted March 02, 2009 - 05:25 AM

#14

so is it a proven good thing or wifes tail bad?

  • scalejockey

Posted March 02, 2009 - 05:59 AM

#15

From the quick reading I've done before bed, it appears that the resistor is good for increasing the duration of the spark. This is because the coil produces a certain amount of energy, resistor or not. With the resistor in place, this discharge of energy is slowed down, allowing for a longer spark duration. However, this is at the cost of a slightly weaker spark. The reduction in current also greatly reduces electrical interference.


Reading along this is the answer that i was waiting for....you got it!

Years ago before cars made like a million volts at the spark, You could foul a plug on one cylinder. The trick was too pull that wire off the plug slightly to bring it back to life or see it would "light up".Thus by using more resistance.

  • Rman of 237

Posted March 02, 2009 - 06:33 AM

#16

From the quick reading I've done before bed, it appears that the resistor is good for increasing the duration of the spark. This is because the coil produces a certain amount of energy, resistor or not. With the resistor in place, this discharge of energy is slowed down, allowing for a longer spark duration. However, this is at the cost of a slightly weaker spark. The reduction in current also greatly reduces electrical interference.

Sounds like a pretty solid answer to me.:p

  • Owyhee

Posted March 02, 2009 - 08:01 AM

#17

I replaced mine a few years ago and haven't noticed a difference. :p

"O"

  • martinfan30

Posted March 02, 2009 - 12:08 PM

#18

Don't worry about it. They rarely fail.

  • zx12r

Posted March 02, 2009 - 01:45 PM

#19

i have a cr500, it calls for resistor plugs. the PO used non r-plugs, so i did also (he said it seemed to start easier). a year after riding the bike it started to foul plugs (still ran great though). after much searching i narrowed it down to the cdi (can't really test a cdi). went to my local honda shop, and the parts guy gives me a price of $350 for a new cdi in 1987(no returns on electrical parts). you know your in trouble when the parts guy says "SHIT THATS EXPENSIVE". i talked to the mechanic and he asked if i used a r-plug. it was the fact that me and the PO used non r-plugs that probably caused the cdi to go bad, it took a couple years though. so now if it calls for a r-plug thats what i use, a expensive lesson. i would think the resistor in the cap would be the same.

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  • thestuz

Posted March 02, 2009 - 05:49 PM

#20

it is a very good question for which i wish i had a intellectual answer.





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