What’s the real engine temp for m8
Thread Starter
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Stage IV
Joined: Apr 2025
Posts: 4
Likes: 1
What’s the real engine temp for m8
2019 road king special thinderheader and air filter with tuner. Ok so Ive been looking forever and can’t seem to find any real info on what the actual running engine temp for the m8 motors are. They say 230-260. I have always had the oil temp dipstick but that is a different temp than engine temp. I never worried as it never hit 200. After getting a pv2 runner and deciding to leave it on the bike for more gauges on my road king I have noticed standard running down the road temps to be 270. If it’s hot out or I am sitting in traffic on a 70-80 day I can see it go as high as 315. Bike doesn’t seem to be any hotter than it ever ran before. At what point is the temperature an actual concern. So many people say oh my bike runs cool at 210 but are going off oil temp not engine temp. Being unless you run a runner that gives you an actual engine temp reading most have no clue what the bike runs at.
Seasoned HDF Member
Joined: May 2018
Posts: 5,814
Likes: 7,147
From: Las Vegas
Most don't care. It's an air cooled engine, it doesn't care either. I've been in extreme heat with no issues and no worries and it's been just fine.
Seasoned HDF Member
Joined: Aug 2006
Posts: 24,531
Likes: 30,855
From: Pennsylvania
All depends on where you are taking the temperature reading from:
1. Head
2. Cylinder
3. Base of cylinder
4. Oil temp before going into oil cooler
5. Oil temp after oil cooler
6. Oil temp in sump
7. Exhaust at head exit.
Engine will withstand most any temp, it will go up and down depending on air flow, speed and RPM the engine is running at.
I take the Alford E. Newman approach; What Me Worry?
1. Head
2. Cylinder
3. Base of cylinder
4. Oil temp before going into oil cooler
5. Oil temp after oil cooler
6. Oil temp in sump
7. Exhaust at head exit.
Engine will withstand most any temp, it will go up and down depending on air flow, speed and RPM the engine is running at.
I take the Alford E. Newman approach; What Me Worry?
Thread Starter
|
Stage IV
Joined: Apr 2025
Posts: 4
Likes: 1
tuner typo
i bought the bike with everything already done. Had to replace top end gaskets at 9k cause head gasket blew out. Bought the tuner because intending on doing cams. Just recently mounted on the bike permanently now I see engine temp on tuner gauge.
i bought the bike with everything already done. Had to replace top end gaskets at 9k cause head gasket blew out. Bought the tuner because intending on doing cams. Just recently mounted on the bike permanently now I see engine temp on tuner gauge.
Thread Starter
|
Stage IV
Joined: Apr 2025
Posts: 4
Likes: 1
All depends on where you are taking the temperature reading from:
1. Head
2. Cylinder
3. Base of cylinder
4. Oil temp before going into oil cooler
5. Oil temp after oil cooler
6. Oil temp in sump
7. Exhaust at head exit.
Engine will withstand most any temp, it will go up and down depending on air flow, speed and RPM the engine is running at.
I take the Alford E. Newman approach; What Me Worry?
1. Head
2. Cylinder
3. Base of cylinder
4. Oil temp before going into oil cooler
5. Oil temp after oil cooler
6. Oil temp in sump
7. Exhaust at head exit.
Engine will withstand most any temp, it will go up and down depending on air flow, speed and RPM the engine is running at.
I take the Alford E. Newman approach; What Me Worry?
im aware of the fact that air cooled motors alter temperature depending on conditions. The question was does anyone know the average running temp or at what point it becomes dangerous to components.
this is why I ain’t ever used forums in the past cause nobody actually reads and responds to the questions always just opinions and trolls.
appreciate the attempt to be useful contributor
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Seasoned HDF Member
Joined: Aug 2006
Posts: 24,531
Likes: 30,855
From: Pennsylvania
im aware of the fact that air cooled motors alter temperature depending on conditions. The question was does anyone know the average running temp or at what point it becomes dangerous to components.
this is why I ain’t ever used forums in the past cause nobody actually reads and responds to the questions always just opinions and trolls.
appreciate the attempt to be useful contributor
this is why I ain’t ever used forums in the past cause nobody actually reads and responds to the questions always just opinions and trolls.
appreciate the attempt to be useful contributor
2. As a new contributor with 3 posts in you may not get the response you wanted; however, hang in there as there are many folks here with years of experience that may be able to provide the information you seek.
3. It may be useful to go to the new users section and introduce yourself, tell us where your are from, and how many years you have been riding: https://www.hdforums.com/forum/welcome-area-only-4/ Pictures of your bike are always appreciated.
4. A good input will generate a good output, the average running temp varies depending on the bike, year model etc. so you will not get an definitive answer.
5. You may want to go here and review DK Customs Videos and reports as they have done some testing: https://www.dkcustomproducts.com/why...cl-tc-dn-1.htm
6. Your attention is invited to the note below.
NOTE:
The above information, while credible, is worth what you paid for it and should not be considered gospel.
Do due diligence, research and have a H-D Field Service Manual before working on your bike.
You will probably have many opinions and suggestions presented; make sure you research the person providing the helpful information as there are some who provide good information that is useful and some who speak out of other orifices with gibberish. You will figure out this quickly.
Last edited by CoolBreeze3646; Apr 28, 2025 at 07:12 AM.
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Thread Starter
|
Stage IV
Joined: Apr 2025
Posts: 4
Likes: 1
1. Forums are what they are, you get both the good and bad, it is up to you to ferret out the responses.
2. As a new contributor with 3 posts in you may not get the response you wanted; however, hang in there as there are many folks here with years of experience that may be able to provide the information you seek.
3. It may be useful to go to the new users section and introduce yourself, tell us where your are from, and how many years you have been riding: https://www.hdforums.com/forum/welcome-area-only-4/ Pictures of your bike are always appreciated.
4. A good input will generate a good output, the average running temp varies depending on the bike, year model etc. so you will not get an definitive answer.
5. You may want to go here and review DK Customs Videos and reports as they have done some testing: https://www.dkcustomproducts.com/why...cl-tc-dn-1.htm
6. Your attention is invited to the note below.
NOTE:
The above information, while credible, is worth what you paid for it and should not be considered gospel.
Do due diligence, research and have a H-D Field Service Manual before working on your bike.
You will probably have many opinions and suggestions presented; make sure you research the person providing the helpful information as there are some who provide good information that is useful and some who speak out of other orifices with gibberish. You will figure out this quickly.
2. As a new contributor with 3 posts in you may not get the response you wanted; however, hang in there as there are many folks here with years of experience that may be able to provide the information you seek.
3. It may be useful to go to the new users section and introduce yourself, tell us where your are from, and how many years you have been riding: https://www.hdforums.com/forum/welcome-area-only-4/ Pictures of your bike are always appreciated.
4. A good input will generate a good output, the average running temp varies depending on the bike, year model etc. so you will not get an definitive answer.
5. You may want to go here and review DK Customs Videos and reports as they have done some testing: https://www.dkcustomproducts.com/why...cl-tc-dn-1.htm
6. Your attention is invited to the note below.
NOTE:
The above information, while credible, is worth what you paid for it and should not be considered gospel.
Do due diligence, research and have a H-D Field Service Manual before working on your bike.
You will probably have many opinions and suggestions presented; make sure you research the person providing the helpful information as there are some who provide good information that is useful and some who speak out of other orifices with gibberish. You will figure out this quickly.
yeah I have never been the one to look at someone’s background before giving advice or information to when asked. I don’t think it should matter if my profile says I’ve been rebuilding dirt bikes and cars and machines since I was 12 and have 30 years of experience. I guess it is what it is this was kind of a last checking spot for any relevant information because Harley’s don’t tell you nothing their techs don’t give you anymore information than the internet. Hell my good friend and brother is a master Harley tech and he couldn’t even give me the full breakdown on it. **** in the wind and get pissed on right. Guess we will see if she makes it to Cali and back in the next couple months. Already doing a tank lift this week just to get some better airflow over the motor and swapping to the upgraded oil pump from the pre 2020 version. Think that should get me 10-15 degrees cooler and make me a happy camper.
stay good my guy
Seasoned HDF Member
Joined: Sep 2008
Posts: 14,160
Likes: 11,249
From: San Diego, CA
I haven't saved any specific references I can share..... but here is what I have always been told.
Not specific to the M8, but for air cooled motorcycle engines in general...
As to oil temps:
Synthetic oils start to degrade at 300° and mineral oils start to degrade at 275°. If I was an avid temp watcher with an oil temp gauge, unless in an emergency, I would avoid letting my oil reach those temps. If the oil gets hot enough to break down, that can't be good for lubrication needs.
FWIW... last year I took a 12 day, 3300 mile trip. I changed the oil about 100 miles before the trip. The trip started with two days of 105° desert heat. It ended with two days of 110°+ desert heat. I changed my synthetic oil as soon as I got home...
As to temps at cylinders or heads:
I have always heard that 400°+ is entering the danger temp zone. Some will say 350°+ and it's time to stop and let things cool off. I have been told that approaching 500°+ is when gaskets fail, heads warp, and numerous other bad things can easily happen.
Sorry I couldn't offer more than years of hearsay. As someone who has worked as a backyard mechanic around boat, motorcycle, car & truck engines since the early 70s, I use these limits unless I hear newer info on the specific engine I am running.
Last edited by hattitude; Apr 28, 2025 at 09:19 PM.
