Keep in mind I don't keep my bike outside, she has a nice garage. Cold starts can still be a pain for me as I live in Seattle though so....
Overall - I noticed a better running bike with the Iridiums. Yes, better cold starts. I didn't get as loud of a pop on startup as I did with the OEM plugs (when she sits overnight the next morning can result in a pop-backfire on initial startup especially in cold weather).
I can not say I felt an increase in HP but a slightly smoother run through the RPMs was noticeable to me.
I did the Nology coil, plugs and wires all in one shot so that made even more of a difference. Again, I can not speak to HP gains as I don't think this is a HP upgrade but overall a better running bike was noticeable. Easier starts, better revs through the RPMs. Similar to upgrading to the Iridiums but better.
In short my non-professional, no dyno runs impressions is that if you can afford the upgrade the aftermarket ignition system upgrades are a nice to have but not a must have. Ill say that it does make the bike run better.
If your strapped for cash but can afford a couple nicer plugs Iridium), do it.
Oh....FWIW - My Montero Sport runs iridium plugs and they only get changed every 100K.
SOLD: 07 Black BA, 39mm FCRs, TPUSA stage 1 head, TPUSA 813 cams, TPUSA 10.8:1 pistons, TTP #3 igniter, Specialty Spares Long Cannons, Tsukayu Hard Bags. 82HP/55tq
NEW: 19 Goldwing Tour DCT
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