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Small update for today, I pulled the Thunderheader so I can give the whole engine a good cleaning after the snowy trip to WI last spring. I noticed the front sensor is really covered in carbon while the rear was clean except for the base, any thoughts on that?
While I'm at it, I'm removing the spacers I had added to the Thunderheader bracket. I used to run a pair of 14" Legends out back and when I installed them, I had serious contact with the pipe. @Mchad had the fantastic idea to push the bracket out with spacers and it's worked for years. This last spring I switched to 13" Bitubo's so I don't need them anymore. This will also let me get rid of one of the last non-ARP bolts on the bike, since I didn't have the clearance with the spacer in place.
Small update for today, I pulled the Thunderheader so I can give the whole engine a good cleaning after the snowy trip to WI last spring. I noticed the front sensor is really covered in carbon while the rear was clean except for the base, any thoughts on that?
While I'm at it, I'm removing the spacers I had added to the Thunderheader bracket. I used to run a pair of 14" Legends out back and when I installed them, I had serious contact with the pipe. @Mchad had the fantastic idea to push the bracket out with spacers and it's worked for years. This last spring I switched to 13" Bitubo's so I don't need them anymore. This will also let me get rid of one of the last non-ARP bolts on the bike, since I didn't have the clearance with the spacer in place.
What tuner are you using and do you have a recent Data log that we can look at as well as the tune?
As I recall, the rear cyl usually runs a little hotter, but Id add both O2 sensors to one of the instrument data pages on the PV and run a 20 min log, starting cold. Then give FM a shout and send them the log.
Edit: do you have 18mm bungs on your pipe? I doubt it but if you do I can always lend you my wideband kit for more detailed logging?
Easy enough to data log from the PV-2 and save it to your computer, then post it to the thread.. Don't really need a copy of the tune but it does help..
I just realized that those are narrow band sensors so they won't be able to record any AFR outside of the narrow band sensors capability of 14.3 -15.1 I believe.. But at least it will show the changes in the VE tables. It would help a lot to see your tune..
EDITED: what do the plugs look like??
Last edited by 98hotrodfatboy; Dec 23, 2025 at 04:09 PM.
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