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Discussion Starter #1
Next time you're over on the right side of your 2017-2019 D390, take a look at the rubber heat shield [flap?] covering the right side of the radiator, also encompassing the right side of the "oh wow, an open-frame fan".
Mine was being held forward, against the radiator, by the clutch cable, and also by a 'drain hose' I have since relocated behind the Y-shaped front engine hanger (so that I could roll that rubber flap back).


The picture I've included from the 2019 engine spare parts catalog isn't truly accurate, but I posted it in case it helps you to envision how that flap is actually mounted in the Duke, via the upper radiator mounting bolts (#29).
And the reason I say the picture isn't absolutely 'accurate' is because... it still includes a picture of that old style fan, pn 93535041044 -- the one that had a closed frame, except for where the air blew out the bottom (and the bottom of the left side).
See the included picture, it is NOT what came on the 2019 Duke I got. In fact, the only place on the 2019 fan where there is even a 'hint' of a closed frame is at the very top center; the rest of the fan is open frame.


Anyway... the reason I was bringing this up is because [I'm a moronic trusting sort, for no good reason]. And all the way up to the first oil change, at 327.5 miles, I thought "I wonder why that fan runs so much". I mean, every time I stopped in traffic... or even if I slowed down around Five Guys Burgers in a parking lot. On.. still on.. stuck on?.. on again?


Was I gonna just go on trusting again? Nah.


Ever since I pulled that flap back, exposing the entire right side of the radiator to full time airflow, I can blast up a state road for 10-15 miles, pull up to a light... and hafta 'wait' a good while before the fan decides it needs to cool anything down. It shuts off pretty quick thereafter, too. Makes me wonder why I was letting it hold all that heat in the radiator and engine; also makes me wonder how much I really like doing head gaskets on a bike rather than riding it.
I rolled it back, punched a small hole through it and tied it back to the trellis frame with a white zip tie.


In one of the pictures, I've outlined the total area that flap was covering, in red. For reference, that flap was actually 'tucked in neat' to the right side where the fins meet the right side end tank. Not even 80 mph gusts on the Interstate were gonna blow that flap open, get it?


The only thing I can figure is that [they; aliens] were trying to enhance the amount of airflow out of the fan onto the hot exhaust manifold, but I mean 'come on, really?!?' And I know that flap is also intended to keep manifold and radiator heat off the ABS unit (which it still does, the way I've got it tied back)...


But you decide -- would you rather your bike say "Ahhhhhhhh"... or would you rather have your fan and engine saying "For the luvva GOD, somebody HELP ME!!!!"
 

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I live in the U.K. and the fan on my Duke 390 rarely comes on.
I am truly jealous of the weather you have and would willingly trade a fan that ran all the time for some warm riding conditions
 

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Discussion Starter #4
But I don't want a fan that runs all the time.. So I guess that means 'no trade', right? >:D
Ok, so I was trying to be funny, dude.. but now I'm thinkin' you're serious (and I'm a jeRk:rolleyes:).


I'll also try not to turn this into a 'gratitude for all we already have makes us healthier' thing... (even tho that's true. well, unless you're busy actively rejecting yourself, or holding out for a better offer you might just make yourself in the future:D). I mean, right?


But to be quite blunt, where I live isn't any picnic. It's downright humid, most of the time...
I bicycled in 48F weather 4 nights ago, and as I'm sure you're aware, humidity actually intensifies body heat loss when it's cold out.
I ride at night. It's my meditation.

Time for balaclava... because I'm not giving up biking; I can't.


A really good contrast to that: I used to live in Colorado Springs, but it wasn't humid there (we were at 6300 ft). It could be 40 degrees out with snow piled up all over the place, but you could still run 100 yards to the neighbors house in nuthin' but shorts, not even shoes, and be completely un-phased by it.;)
 

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If I understand correctly what you have done, it would indeed make the radiator flow more air when not using the fan, at the expense of losing ducting which makes the fan pull much more air through the radiator when the fan DOES run.

So, it would make the fan not come on as much, but could lead to overheating when you really need the fan.
 

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Discussion Starter #6
No... there is no ducting. The fan is a very close interface to the radiator, and that flap on the right simply prevents air flow 'out of the fan' to the right, (but it also prevents airflow 'through the right side' of the radiator).


In summary, having that flap in its original location does not enhance cooling of anything.


Look at the pics again, then look at your bike veh-wy cwose-wy. You'll see what I mean.
 
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