Running HOT! In the cold.

Discussion in 'Mechanics Garage' started by DanBjR, Mar 22, 2020.

  1. DanBjR

    DanBjR New Member

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    So I've read about the bike running hot and obviously its somewhat expected. However today I was out working on my basic skills in a large open lot, air temp 34°F, and noticed the bike at 240°F and no fan.

    Prior owner installed an override switch and that got me down to 180ish. Alot of starts and stops, mostly 1st and 2nd gear, speed 25mph and under. Ok, so that's kinda expected I guess. But then going down the road and I'm still seeing near 185 and its freezing outside.

    So should I be worried about the temps and what should I look for in terms of the fan activation? I'm unfamiliar with the bypass mod and was told it still ran auto when the switch is off.
     
  2. bk94si

    bk94si Member

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    Sounds like the fan switch is bad.
     
  3. DanBjR

    DanBjR New Member

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    I hope that's all. In the meantime will it hurt to leave the fan running? Obviously I'm trying to be vigilant but for a new rider I've got enough to be paying attention to. I dont want to be fiddling with the override switch constantly nor watching the gauge instead of the road.
     
  4. Diving Pete

    Diving Pete Insider

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    I suspect the previous owner installed the switch rather than buy a new thermo-switch to fix the issue.
     
  5. DanBjR

    DanBjR New Member

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    Not sure about that. I actually discovered the bikes first owner was a member here, porcupine73. Was reading though the rwb production numbers thread and found my vin. According to one of his posts he bypassed the fan year one.

    Obviously given the bypass its possible the switch went bad and was unnoticed. I cant hear the fan unless I'm at idle anyway.
     
  6. raYzerman

    raYzerman Insider

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    Thermostat controls most of it to a point... usually starts to open at ~180, full open at ~205If you're not moving at speed, it's normal to run hotter as there isn't enough airflow through the rads. Your coolant shouldn't boil until around 265 but if over 200 I'd switch on the fan... best fix that coolant switch, maybe he bypassed it rather than having it in series in the switch circuit. I'd want it to come on auto with a manual override personally... maybe check how it's wired up. IIRC, fan comes on ~210-ish. shuts off ~200-ish.
     
  7. GreginDenver

    GreginDenver New Member

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    If your bike's thermostat is failing, as in: the thermostat is seized up or binding and not moving to the "open" position as the coolant heats up, then there will not be any coolant circulating through the radiators for the prior-owner Jerry rigged "always-on" fan to cool.

    You can't cool the fluid if it isn't circulating through the radiators... even if you run the radiator fan.

    One of the common old-age-related failure modes of a VFR thermostat is: thermostat fails to move completely through its normal (original) range-of-motion. Instead of moving through its normal range-of-motion the thermostat mechanically binds or seizes up prior to going completely open, or the thermostat's expanding-wax-element simply doesn't expand or contract like it used to do.
     
  8. DanBjR

    DanBjR New Member

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    Thank you, it seems to me the obvious course of action is to replace the thermostat, given the age, mileage, and lack of maintenance records I feel like it's better to be safe than sorry.

    Is there anyway to confirm temp sensor operation besides just checking resistance? Obviously I'm going to have to dig into the bike and check the connections. There are a number of buttons and switches that have been added so I'm not sure if maybe in addition to the bypass switch theres one for shutting off the auto entirely.

    I know theres two modulators but I've got 1 momentary and 2 on/off switches that I'm not sure what actually do.
     
  9. Diving Pete

    Diving Pete Insider

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    Really easy with a multimeter - once the engine is at about 106C / 230F the fan should switch on. The switch creates a circuit to earth which turns the fan on. They do go bad HOWEVER I'd be looking at how the PO connected the switch - for all you know he disconnected the auto side of it..
     
  10. DanBjR

    DanBjR New Member

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    I think I'm going to order the switch and thermostat, given the relatively inexpensive cost, and then pull it apart and try and diagnose the issue.

    I figured I can also trace the wires coming off the switches that have been added to get those sorted as well. I also noticed the other day that the headlight/taillight modulators are just spliced and taped. God knows that's a problem in the making. I really hope theres not a lot of electrical issues to be found.
     
  11. squirrelman

    squirrelman Member

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    often overlooked, the rad cap can go bad and fail to hold pressure, leading to overheating. try replacing it, and keep an eye on the coolant level under the cap, not in the overflow bottle.
     
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