M8 Engine Temps
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Road Captain
Joined: Jul 2008
Posts: 601
Likes: 109
From: San Diego
M8 Engine Temps
Breaking in new '18 RKS and I was surprised to see much higher temp engine and head temperatures on Road King Special. At one point engine temp read as high as 315F and head temp at 345F. Ambient temps this time of year here is about 85F.
I remember, my former '14 FLHTK Project Rushmore, would register as high as 250F engine temp and 300 head temp...
Looks like my oil cooled M8's is running much hotter than my wet head Rushmore...any else observes this same temps on your oil cooled M8s?
Also, the drive belt is so tight, almost no slack at all.
I remember, my former '14 FLHTK Project Rushmore, would register as high as 250F engine temp and 300 head temp...
Looks like my oil cooled M8's is running much hotter than my wet head Rushmore...any else observes this same temps on your oil cooled M8s?
Also, the drive belt is so tight, almost no slack at all.
Last edited by DC2009EGUC; Oct 27, 2017 at 08:24 PM. Reason: Corrections
Stellar HDF Member
Joined: Feb 2013
Posts: 2,325
Likes: 333
From: Upper Providence Pa
Yes, these are normal numbers... I have a twin cooled M8 and my head temp can go as high as 350+ on a 95 degree day and high rpm (riding it in the 40/5500 range) but they quickly come down in the lower rpm's Yes they run hot... if you see 400+ temps, be concerned
Elite HDF Member
Joined: Nov 2010
Posts: 3,846
Likes: 173
From: Simi Valley, CA
I just got a twin-cooled Ultra Limited a couple weeks ago. A few days ago we had a 105+ degree day here in Southern California. I checked some temperatures (cylinder heads, cylinders, crankcase, oil pan, trans housing, coolant lines) immediately at the end of that ride with an infrared thermometer and didn't see anything over 260 degrees.
Tourer
Joined: Oct 2008
Posts: 340
Likes: 26
From: South Texas
I too see those numbers here in South Texas. I have been considering going to a different air cleaner to try t get my IATs down. When the charge air is already 150F the motor can’t help but heat up. Wondering if anyone with a heavy breather / Hog snout AC may help with IATs better than the high flow which seems to pick up heat by being closer to the engine?
just a theory I have been investigating. Any thoughts here?
just a theory I have been investigating. Any thoughts here?
Seasoned HDF Member
Joined: Sep 2009
Posts: 17,148
Likes: 6,170
From: SE Michigan
spec on drive belt deflection is 1/8" @ 10 lbs if I recall correctly, mine seemed tight, tech said all good at 5K service
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Road Master
Joined: Jan 2016
Posts: 1,143
Likes: 433
From: Menifee, CA
Drive belt tension on my new 2018 RGU was way tight. I gave it 1500 miles to stretch, and it did stretch, but not enough. At 1500 miles, it was still 1/4" at the tight spot. The correct deflection range is 3/8" to 9/16"
To make it easier for my simple brain to grasp, I convert the 3/8" to 16ths, which equals 6/16" so we are dealing only with 16ths. So, the book range is 6/16th to 9/16th.
Two things are critical here. First, when checking belt tension, the engine and frame must be at ambient temp. As the bike heats up, the belt gets tighter. The belt tension spec is for a cold bike.
Second, all belts will have a tight spot and a looser spot, or spots. You gotta locate the tight spot and adjust to that.
Add a third: Bike weight must be on the wheels, and no extra weight on the bike, so unload the saddlebags before doing this.
Also, bike must be in neutral.
It is hard to roll the bike back and forth to locate that tight spot, so I do it on my J&S. I locate the tight spot, mark it, check tension, and adjust if necessary. My bike will lose about 1/16" of deflection when weight goes back on it after I lower it to the floor. Therefore, when checking tension with bike off the ground, add 1/16" to account for that. That works for my RGU, but you should check yours to make sure it acts the same.
To make it easier for my simple brain to grasp, I convert the 3/8" to 16ths, which equals 6/16" so we are dealing only with 16ths. So, the book range is 6/16th to 9/16th.
Two things are critical here. First, when checking belt tension, the engine and frame must be at ambient temp. As the bike heats up, the belt gets tighter. The belt tension spec is for a cold bike.
Second, all belts will have a tight spot and a looser spot, or spots. You gotta locate the tight spot and adjust to that.
Add a third: Bike weight must be on the wheels, and no extra weight on the bike, so unload the saddlebags before doing this.
Also, bike must be in neutral.
It is hard to roll the bike back and forth to locate that tight spot, so I do it on my J&S. I locate the tight spot, mark it, check tension, and adjust if necessary. My bike will lose about 1/16" of deflection when weight goes back on it after I lower it to the floor. Therefore, when checking tension with bike off the ground, add 1/16" to account for that. That works for my RGU, but you should check yours to make sure it acts the same.
Road Master
Joined: Mar 2017
Posts: 760
Likes: 273
From: Olympia, WA
Breaking in new '18 RKS and I was surprised to see much higher temp engine and head temperatures on Road King Special. At one point engine temp read as high as 315F and head temp at 345F. Ambient temps this time of year here is about 85F.
I remember, my former '14 FLHTK Project Rushmore, would register as high as 250F engine temp and 300 head temp...
Looks like my oil cooled M8's is running much hotter than my wet head Rushmore...any else observes this same temps on your oil cooled M8s?
Also, the drive belt is so tight, almost no slack at all.
I remember, my former '14 FLHTK Project Rushmore, would register as high as 250F engine temp and 300 head temp...
Looks like my oil cooled M8's is running much hotter than my wet head Rushmore...any else observes this same temps on your oil cooled M8s?
Also, the drive belt is so tight, almost no slack at all.
