Rear cylinder excessive heat
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Road Master
Joined: Sep 2007
Posts: 963
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From: Displaced hillbilly
Rear cylinder excessive heat
I have an 08 Street Glide, original owner, engine is completely stock except for stage 1 intake, Vance & Hines Dresser Duals, and V&H Eliminator 400 slip-ons. A few months ago I didnt think it was running as well as it could, wasnt getting very good mileage, so I purchased an FP3. Flashed a map, and after some auto tune sessions, bike runs great and mileage is better than when I bought it. The last few months though Ive noticed it seems to be really running hot, especially from the rear head. I purchased a laser infrared thermometer so I could see what kind of temps Im getting. On the front (measuring right about the spark plug) Im getting around 230 cruising (90 air temps outside) which is usually within a degree or two of what it shows on the sensor data screen on the FP3 app. The rear temp though is in excess off a 100 degrees higher or more. I was under the impression that while the rear will obviously run hotter than the front, it was supposed to be somewhere in the neighborhood of around 20 degrees. If this outside the norm, what is going on to cause this issue? Other than this, the bike really seems to run great, just getting tired of baking while riding.
Grand HDF Member
Joined: May 2014
Posts: 3,843
Likes: 1,174
From: florida
most likely running too lean on rear cylinder,,,several different posiblitlies, vacum leak, low comp, or god forbid the auto-tune made the rear too lean,,,,maybe sensor weak or failing during auto tune process, check the basics first and rule them out, then try to check 02 sensor response and performance,,,maybe replace the rear 02 then auto tune again.
m
ps make sure that your fuel pressure is good also!
m
ps make sure that your fuel pressure is good also!
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Road Master
Joined: Sep 2007
Posts: 963
Likes: 145
From: Displaced hillbilly
Well I went for a ride today and setup the FP3 to monitor the O2 sensors. The front would fluctuate quite a bit, but the rear seemed to hold pretty steady at .9, only changing occasionally if at all. Thinking this might be the issue. Wouldn’t .9 indicate a rich condition to the ECM causing it to try and lean it out, which in turn create the heat I’m feeling?
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,071
Likes: 1,006
higher number the more fuel in the ex since there is less oxygen. the sensor maybe locked and is toast. swap with the other and see if issue follows. the rich condition would tend to lower the temperature.
a normal o2 will float around but avg around .6. the ecu is probably trimming as much as it can so there should be a code thrown.
a normal o2 will float around but avg around .6. the ecu is probably trimming as much as it can so there should be a code thrown.
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