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Iridium spark plugs in vintage bikes

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I installed a new NGK Iridium plug in my TS250 yesterday and although it ran, it had a loss of power, installed the conventional NGK plug and the whoo-hoo came right back.

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i switched to Denso plugs 30 years ago when they introduced the u groove electrode, and that's all i run in all my stuff. i've put about 13k miles on an iridium u groove plug in my drz with no problems, and i just put a set in my 98 dodge ram, also with no problems. i know ngk has a good reputation, but i had fouling problems with ngk's in an rd350 that went away with the switch to densos(Nippon Denso back then). Good Luck!

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You'll find that its hard to beat a basic copper core spark plug. Iridium's and all the fancy stuff last longer, but they don't necessarily burn as hot. And a vintage bike needs as hot a spark as you can get.

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Much of the spark plug "advancements" have been in marketing materials, IMHO. There really isn't that much of a difference in the function to make it worth the additional expense.

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With some vintage ignitions, I've found it's really important not to use resistor plugs, especially when the bike already has a resistor-type plug cap. NGK indicates resistor-type plugs with an R in the plug designation; I haven't figured out Denso's numbering system.

Ray

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Just my humble opinion - I think the new iridium plugs in a systems that uses contact breaker points is all for naught. They were designed and run better off the conventional type spark plug. I installed a NGK B8ES into the TS250 and it was a happy camper, like I said in the original post it ran off the iridium plug but seemed sluggish.

I have run Iridiums in my XR650L and XR250R and noted no difference at all. I just installed a set in my HD Dyna and will see.

Replaced the plugs in my 06 Tundra with ND Iridiums and it liked em alot!

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