Let's talk tempertures

Discussion in 'Touring Models' started by Retrop, Jul 4, 2009.

  1. Retrop

    Retrop Active Member

    I know that many out there are constantly worrying about burning up their bikes when the outside temperatures get high. Personally, I feel like the vast majority worry needlessly about this. The engineers who design engines understand the principals involving metals and temperatures and design accordingly. This paranoia with heat that many have is making a lot of people very rich. I am not saying we need not worry about heat, because it should be a concern, all I am suggesting is that we need not let it get out of hand. Run good, high quality lubricants. Full synthetics are probably the best thing to do to promote a happy engine. They start to break down at a higher temperature range than dino oils. So, if you do get caught short some time and find yourself trapped in stop and go traffice it is comforting to know you have a crankcase full of high quality synthetic lubricant. They are a good thing. We should all be running a synthetic gear oil in the transmission too. Anything from a 75-90 wt or maybe a 75-140 if you ride in really hot weather is just plain being cautious.

    OK, having said all that, just for gibbles today I checked some of the temperatures on my 09 Touring bike just as I pulled into the garage after a 4 hour ride. The outside ambient air temperature was 104 degrees. Humidity- 37%. We were riding at a constant 70 mph on both concrete and asphalt highways. No stop & go riding.
    To check the various temperatures around the bike I used an infrared, digital thermometer from a distance of 3 inches. The thermometer is known to be spot on, so I feel like I a got accurate readings. The beam was pointed to "black" paint, not shiny surfaces.

    1st reading: Next to the spark plugs-201.5 degrees farenheit.
    2nd reading: Half way down the jugs-188 degrees.
    3rd reading: At bottom of jugs-181.5 degrees.
    4th reading:Bottom of crankcase, next to the oil plug-205 degrees.
    5th reading: Several locations on bottom of crankcase-201 degrees.
    6th reading: Center of front tire-126 degrees. Two inches to the side-134.
    7th reading: Center of back tire-120 degrees. Two inches to the side-125.
    Why was it hotter two inches from the center of tire? I don't know, unless it is because the D407 tires have a different compound in the center this year. Maybe some "real, school educated engineers" can chime in here).

    All readings were taken within 60 seconds after parking so there was not much cooling. If anything, temps can sometimes rise a bit, immediately after turning off the engine.
    What we see here is that the temp next to the spark plugs (201) is about the same as it is at the bottom of the crankcase (205) where you would drain out the oil.
    This temperature range is well within what most good dino oil is speced out at today. Synthetics specs are even higher,upwards to 275 degrees+.
    Disclaimer: I do run a fuel management device. TFI brand, for whatever that is worth. I just use it, I don't work for them.

    So. relax. Put good lubricants in your bike and just ride. All I am saying is most of this add on equipment which is supposed to cool off a hot bike probably can't hurt anything, but the person who really benefits the most is not you, but the person who is selling it. Engines are supposed to run hot, there is fire down there, after all. It is supposed to feel hot to the touch when we touch our finger (98.6) to them. Any comments? Let er rip.
  2. LIRider

    LIRider Account Removed

    The fact that you have a TFI has a lot to do woth your reduced temperatures. Althought it is for perfromance, it is also an "add-on" for reducing temperatures by getting rid of that factory lean condition.
  3. eleft36

    eleft36 Junior Member

    Your next to the spark plug is about 150*shy of reality.
    Most air cooled engines, Harley's included, while in motion will have a head temperature between 230 and 250. That's not next to the spark plug which is close to 360*.

    Digital laser thermometers read different on different colors and textures.

    Think about it, combustion temperature is 450* to 580* F

    And how close is the spark plug to the combustion event?

  4. glider

    glider Veteran Member

    I agree with Al here. How could the head temp next to the plug be lower than the oil temps right over the combustion chamber?
  5. Retrop

    Retrop Active Member

    I shot the outside of the fin next to the spark plug. I am sure the head temps were higher than 200 degrees. I choose not to measure the temp of the shiny heads, because laser reading on those kind of surfaces tend to be unreliable. My measurements were on black surfaces only.
  6. whatyardwork

    whatyardwork Banned

    I just want to know who the rocket scientist is that descided to put an ambiant temperature sensor on my bike?Did they realy think putting a sensor on a 200 degree bike would give us an accurate reading?
    Gee, Im cold..yep there it is that temp gauge confirms it, Im cold.
  7. eleft36

    eleft36 Junior Member

    Well, there are those who don't believe the obvious:bigsmiley11:

  8. acj2001jones

    acj2001jones Member

    Has anyone ever thought about replacing the ambient air temp. gage with an oil temperature gage? What is the real difference in temperature when changing to a more rich mixture? 10/20°? I am not interested in performance mod's on my stock FLHX, but I do not want it to run hotter than it should. Anyone suggestions on stock temp's?
  9. dolt

    dolt Senior Member Contributor

    I have taken similar measurements with similar instruments on both my bikes which are performance builds. The temps I measured were much closer to the temps in the post by eleft36 than retrop's temps.

    I don't worry about the heat but I don't like heat; it is the mortal enemy of an air cooled engine so I do take all the steps I can to mitigate against the heat.
  10. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

    Agree with eleft36, heat dissipation though the heads is pretty dramatic, and spark plugs have ceramic insulator that keeps the internal temperature isolated from the outside surface "top-side" may affect digital temperature reading if 60 secs or so have stopped since combustion events have ceased.