Cylinder head temps
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Road Master
Joined: Sep 2007
Posts: 963
Likes: 145
From: Displaced hillbilly
Cylinder head temps
Posted over in the engine forum as well, but curious as strictly touring bikes what the average difference in temps between the two cylinders that most are getting.
I have a stock 96 other than stage 1 air intake, V&H true Duals, and V&H 400 slip-ons. Used a infrared thermometer to check right around the plugs and Im seeing in excess of a 100 degree difference between the two. The front is measuring within a degree or two of what Im seeing on the FP3 app, but I think the rear temp is a little higher than what would be considered normal
Bike runs great, but cant help to think there is something going on to cause such a great difference in temps.
I have a stock 96 other than stage 1 air intake, V&H true Duals, and V&H 400 slip-ons. Used a infrared thermometer to check right around the plugs and Im seeing in excess of a 100 degree difference between the two. The front is measuring within a degree or two of what Im seeing on the FP3 app, but I think the rear temp is a little higher than what would be considered normal
Bike runs great, but cant help to think there is something going on to cause such a great difference in temps.
Banned
Joined: Jan 2017
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From: in a cave at the foothills
All things considered why wouldn't there be a difference? I rarely think about it unless I am in parade mode in the middle of summer going nowhere fast such as in tourist traffic. Otherwise I just ride my bikes and give it no thought. I have however known for a very long time that logically the rear cylinder will get much hotter than the front. Nothing going on at all so just ride and enjoy.
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Road Master
Joined: Sep 2007
Posts: 963
Likes: 145
From: Displaced hillbilly
Obviously due to the placement of the rear cylinder it’s going to run hotter than the front, I’m just questioning if a discrepancy of over a 100 degree difference is outside the norm or not. All things being equal and if your stopped in traffic, the front cylinder wouldn’t be getting any air flow as well, so to me it seems there shouldn’t be that big a difference between the two.
Road Captain
Joined: May 2015
Posts: 668
Likes: 72
From: Wisconsin
Also if you use the engine heat deflectors. They shield heat from your thighs. They do that. But also trap the heat. Causes the rear cylinder to get even hotter. Still normal BTW. 
If you keep looking at your stats on the FP3 and alike it's gonna drive you nuts! Great to have a base line so if something is wrong you can see the difference. But? There are negatives as well. Ride safe.
If you keep looking at your stats on the FP3 and alike it's gonna drive you nuts! Great to have a base line so if something is wrong you can see the difference. But? There are negatives as well. Ride safe.
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Road Master
Joined: Sep 2007
Posts: 963
Likes: 145
From: Displaced hillbilly
No heat shield deflectors, so that shouldn’t be a factor. If a 100 degree difference is normal, than fine so be it. I’m not one to overly obsess about something, I just thought that was a little bit of a high difference between the two.
Elite HDF Member
Joined: Nov 2013
Posts: 4,377
Likes: 647
From: Santa Clarita
If it's running good...then ride it. Don't sweat the small stuff. Well known that the rear cylinder runs hotter than the front one...after all it sits behind the front one that gets all the cooler air.
Put the high tech stuff away and ride your low tech motorcycle!
Put the high tech stuff away and ride your low tech motorcycle!
Road Captain
Joined: Oct 2012
Posts: 520
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From: houston, tx
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Outstanding HDF Member
Joined: Sep 2010
Posts: 2,630
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From: Mountain West, Big Sky Country
reduce the difference in temps.
get a tank lift of at least 1.5 inches and install only one side of the plastic heat deflectors so it acts as a scoop vs holding heat in.
will make minor difference while moving, none sitting still.
get a tank lift of at least 1.5 inches and install only one side of the plastic heat deflectors so it acts as a scoop vs holding heat in.
will make minor difference while moving, none sitting still.
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Road Master
Joined: Sep 2007
Posts: 963
Likes: 145
From: Displaced hillbilly
I may have stumbled on to an issue. Took the bike out for a run this afternoon to try and see some readings and set the FP3 up to monitor the O2 sensors. The front fluctuated quite a bit, but the rear seemed to stay pegged right around .9 most of the time. If I understand this correctly, wouldn’t that make the ECM think the mixture was too rich and then try to lean it out? If its a faulty O2 sensor maybe that’s what is causing the rear cylinder to seem so hot
