The LF250-B comes with Torch A7TC plugs as stock, so the NGK part would be CR7HIX. However, the Yahama original engines take CR6HIX plugs.
It's horses for courses here; the '7' plugs dissipate heat faster, which is good if you're doing high speed runs (or idling in traffic), but the '6' plugs will help the engine warm faster on short runs.
I'm on CR7HIX at the moment, but I find the engine's taking longer to warm up and come off the choke than I'd like, so I'll be changing to CR6HIX next pay-day.
