Anyone else running NGK CR9EIX plugs?
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Road Warrior
Joined: Jul 2014
Posts: 1,584
Likes: 520
From: VA
Anyone else running NGK CR9EIX plugs?
I usually stick with stock plugs. But since it's a pain in the *** to change the right side plugs I went with the longer lasting iridium's. I just pulled the left side plugs. They look like the bike is running too rich. Nothing has been changed tuning wise except the plugs. I triple checked the plug part number. Anyone else run into this? Maybe the M8 doesn't like these plugs
HDF Community Team
Joined: Mar 2017
Posts: 7,821
Likes: 4,378
From: Texas
How long was the bike running before the previous shutdown when you looked at the plugs? If not very long (i.e. not up to operating temp), it would most likely be running rich. I've always been told with EFI you don't look at the plugs to know if you're running rich/lean, you look at A/F ratio.
Intermediate
Joined: Jun 2007
Posts: 41
Likes: 12
Twin cams used the plugs to detect knock and most guys ran stock plugs for that reason. The M8s apparently use a separate knock sensor, don't know if the system is tied to the plugs or not though
Last edited by otterhigh2; Oct 9, 2020 at 09:02 AM.
Seasoned HDF Member
Joined: Jan 2008
Posts: 13,490
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From: State of Confusion
I'm all for aftermarket almost anything, but the 3 things on these bikes it's probably not a good idea to get away from stock on are plugs wires and coils. Delphi Harleys use an ion sensing system to retard timing and prevent pre-detonation (knock). The system senses extra ions in the cylinder before the knock and sends feedback through the plugs and wires and it is tuned to the stock plugs and wires. Most don't have a good experience using aftermarket plugs or wires.
Intermediate
Joined: Jun 2007
Posts: 41
Likes: 12
Yeah I just corrected myself
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