Some guys use the non-iridium plugs to get their jetting in the ballpark with a new combination. That way they have many fresh plugs for a cheap price.
Once my jetting is dialed in I put in the proper heat range iridium plug and forget it. I have not touched mine in months.
I'm sure the traditional plugs are fine for play riding. But, compared to the iridium plugs the traditional plugs of a particular heat range foul a bit easier and have poorer resistance to causing pre-ignition knock from overheated electrodes. The traditional plugs electrodes also wear away more quickly.
The projected tip, iridium plugs provide an excellent trade-off between knock resistance and startability. They also allow the flame kernel to grow rapidly away from the electrodes unlike the various multiple electrode plugs out there today(Splitfire and the like).
Some engine builders do index the plugs, but the difference with the TRX450R's pent roof combustion chamber shape should be small. But if every last HP matters go for it!
All that said I've had a bad iridium plug before. It was not visibly fouled but it produced no spark at all. I imagine it was cracked internally or had some other internal defect.
Just one other small thing...it's no big deal at all. But um, I'm not quite sure what you mean by "Iridium is a type of Platinum" they are both elements on the periodical table. They are 2 different types of metal. No worries. :)
2004 TRX450R - Derisi Racing Suspension - 13.5:1 Wiseco piston, Keihin 40mm FCR carb, '06 airbox, ported head, HRC cam
1988 TRX250R - Wiseco Pro-lite 265, Keihin 38mm PWK carb.
2003 XR650R - Uncorked, street legal
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