VF750F Idle Overheat Solution

Discussion in '1st & 2nd Generation 1983-1989' started by Kyle G., Mar 29, 2021.

  1. Kyle G.

    Kyle G. New Member

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    My bike is overall in good condition and is pretty fun and easy to ride, there was one exception though. Prolonged idling, especially in the summer with temps above 80 degrees F would have the temp gauge just keep on climbing hotter and hotter. When the cooling fans inevitably switched on they would take forever to cool the bike back down if they ever did. Naturally in hot weather it wouldn't take long at all for the bike to start overheating. After some humming and hawing for a while I noticed the lower radiator was situated a little too close to the front cylinder exhaust pipes for its own good. At a standstill there is no airflow around those pipes and thus the heat they put out goes straight into heating the lower radiator.

    I didn't want to install a manual switch to turn the fans on earlier as i believe that is just a bandaid and just something else I have to distract myself with. My solution was to fit an auxiliary 12v 120x38mm 'PC' fan to the lower rad and wire it to be switched on with the stock upper radiator fans. This fan flows a lot of air, about 200 cfm worth and is a little louder than the stock fans, but boy does it cool the bike down in a hurry. The temp gauge used to just keep on climbing with just the stock fans, now they stay on for just 30 sec at a time and I have no issues at all letting the bike idle in hot weather. I've had this setup installed since 2019 with no problems, granted I haven't driven the bike through torrential downpours or through flooded streets so I don't know exactly how waterproof the fan is.

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    As you can see, the fan was a perfect fit nestled inside the radiator frame after some light filing on the sides and bottom so as to snap into the radiator. I filed down the top of the fan at a 45 degree angle to fit under the curved steel frame, making sure not to go too far and have the blades exposed. I went pretty slowly on this step repeatedly test fitting it with the radiator to make sure it was a tight fit when fully assembled. After rounding the corners the fan is rock solidly clamped in place with no bolts or zip-ties needed. As for wiring it up, I ran the red wire up the stock wire loom and tucked the bare wire end into the stock fan connector, wiring the new fan in parallel with the existing ones. The black wire goes into the temp switch and is crimped into the black wire bullet connector. The blue pwm wire is just cut short at the fan and left unused. This is the listing for the fan if anyone wants to try this modification out. https://www.amazon.com/Delta-AFB1212SHE-CF00-Cooling-190-48-Tach/dp/B00CIB9BTU
     
    Last edited: Mar 29, 2021
  2. squirrelman

    squirrelman Member

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    not a good idea to overheat an engine by prolonged idling ESPECIALLY in warm weather. cooling depends upon air moving through the raDIAtor (with the bike moving forward), and the small fan is never enough cooling except in cold weather.

    fan switches often fail on older bikes, and a bypass switch is very helpful.
     
  3. VF1000Fe

    VF1000Fe New Member

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    Fan installed in front of Upper Rad (the hotter one).
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    Runs all the time (power'd off Low Beam circuit).
     
  4. squirrelman

    squirrelman Member

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    not good if a bad thermostat or the fan keeps engine below its best operating temp in your cool climate.
     
    Last edited: Apr 2, 2021
  5. Intercepturbater

    Intercepturbater New Member

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    Ok, I've searched on here and further on the internet, but all I've found is a couple broken links. If I could get a link to instructions for the fan bypass switch I would be forever grateful!
     
  6. Captain 80s

    Captain 80s Member

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    Can't provide a link to instructions, but the key is to create the bypass in parallel to the original wiring so the thermo switch can still turn on the fan when it reaches the temperature. If there are 2 wires going to the thermo switch on the radiator, then those wires get connected to turn on fan. If it is a 1 wire thermo switch, then you ground that wire to turn on fan.
     
  7. Intercepturbater

    Intercepturbater New Member

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    Thanks. What do you ground to?
     
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