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Iridium plug. Cap mod.

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  • Iridium plug. Cap mod.

    Hi Folks. After reading here that iridium spark plugs have a built in 5k Ohm resistor, I realised that most suppressor caps also have 5K Ohm resistors. I've run my bike with iridium plugs and the resistor caps with no problems but I wondered if 10k Ohm resistance would compromise the spark in some way. I supposed that, logically, it should do. Non-resistor caps are harder to find and usually look like the one on my lawnmower, so I removed the resistors from my NGK plug caps.

    As has been mentioned on the forum a while ago, the long-reach, angled caps (for cylinders 2 and 3) are easy to do. You just unscrew the brass bit where the plug clicks onto and the resistor drops out, followed by a little spring. I used the spring from a ballpoint pen, dropped it into the space where the resistor + little spring lived and then screwed the brass bit back in.

    The smaller L-angled caps for cylinders 1 and 4 have the resistor in the top part of the L, behind the screw which you put the HT lead onto. The head of these screws is embedded in the plastic/whatever that the caps are made of. I screwed a small piece of wooden dowel onto the screw thread, as far as it would go. Then wiggled it a bit and pulled fairly hard. The brass screw assembly comes out on the end of the dowel, followed by the resistor and small spring. Pop in on ballpoint pen spring, and then push the dowel back in hard to relocate the screw. Then unscrew the dowel.

    Rather stupidly, I removed a plug cap whilst the engine was running and got a huge whack of HT current through my glove, which then earthed through my other gloved hand (which was on the bars) and, amazingly, the sole of my boot at the same time. The last time I got a whack was through the OEM coils with ballast resistor and it definitely didn't feel like that... no way. So, it could be the Dyna coils, or the carbon leads or removing the resistor in the caps... or more likely a combination of all of that. On a serious note, my nurse girlfriend assures me that HT current can stop your heart or cause it to beat oddly. She told me that 8 people a year in the UK die from licking 9v batteries to see if they have any charge. After that whack tonight from my home-made Taser, I'm going to be a lot more careful!
    XS1100F 1980 European model. Standard. Dyna coils. Iridium plugs. XS750 final drive (sometimes). Micron fork brace. Progressive front springs. Geezer regulator/rectifier. Stainless 4 into 2 exhaust. Auto CCT (Venturer 1300) SOLD. New project now on the go. 1980 European model.

  • #2
    Take a hit from a taser once and tell me what is worse.....
    Nathan
    KD9ARL

    μολὼν λαβέ

    1978 XS1100E
    K&N Filter
    #45 pilot Jet, #137.5 Main Jet
    OEM Exhaust
    ATK Fork Brace
    LED Dash lights
    Ammeter, Oil Pressure, Oil Temp, and Volt Meters

    Green Monster Coils
    SS Brake Lines
    Vision 550 Auto Tensioner

    In any moment of decision the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing.

    Theodore Roosevelt

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    • #3
      I run iridiums in both the SF and XJ, stock coils on both, ngk caps on the SF, stock caps on the XJ. No issues I can see.No worries. BTW I firmly advocate iridium plugs. Been in the SF for at least 4 years, never taken them out.
      79SF
      XJ11
      78E

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