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KTM 450 EXC RFS Overheating Solution - Server Fans? Yup!

Joined
Oct 14, 2014
Messages
237
Location
San Antonio, TX
2005 KTM 450EXC with aftermarket oversized gas tanks kept overheating while operating in slow technical conditions in the south Texas and northern Mexico summer heat. This setup should work on just about any bike as long as it has an M14X1.5 bung in the radiator.

I had already installed an overflow tank. It helped but I wanted to take it a step further.

There are no commercial fan solutions available that I'm aware of that will work with the big Acerbis, Safari, IMS, or Clarke gas tanks. I have a stock tank, IMS 3.9 Gallon, and an Acerbis 6.6 Gallon. It works with all of them.

I've been running this setup for well over a year and have done several demanding trips including Big Bend National Park and various places in northern Mexico. Most of the time, temps have been in the high 80s to low 100s. Speeds were often little more than crawl/walk speed. It also included at least a couple hundred miles of 45-70 mph runs down nasty washboarded dirt roads and a couple hundred pavement miles with occasional speeds of 90+. Lots of vibration, lots of hard suspension hits. The fans have been abused well beyond their intended purpose, but they continue to work perfectly!

I've rode through a couple mild rain showers and stream crossings where water sprayed pretty heavy into the fans. Full disclosure here...they were not running at the time. I've never completely submerged them in water, but I have sprayed them with a garden hose while running.

The second fan has never came on automatically while riding or even while idling. The first fan seems to do a great job of keeping things cool enough for it not to be needed. I like having it as a backup though. Just in case.

I'll run down the overall concept and give a parts list at the end.

With the switch in “Standby”, Fan #1 turns on at 195F, fan #2 turns on at 210F. I can't remember the specs, but I think they turn off at about 10 degrees below their turn on temps.
They can both be turned on manually with the switch if desired.

I used a three way, (on-off-on) waterproof, illuminated rocker switch. I used a 10 pin Molex connector behind the headlight fairing to make it easy to remove and re-install the fairing.

The ON position with an Amber indicator light is the “Standby” position.
The ON position with a Red indicator light is the manual “Override” position. The red light also illuminates when a fan turns on automatically.
Off would be my, yep, you guessed it... the “Off” position.
I fashioned a little box out of styrene plastic for the switch and mounted it on the backside of the headlight fairing.

I attached two 120mm x 25mm 175CFM water and dust resistant server fans to the radiators using zip-ties.

These are BMW part numbers that you can order through Amazon or anywhere that has BMW parts. I'm using the higher temp switch, but you can go with the other if you want the fans to turn on sooner.

#61131378412 – plug housing
#61130007445 - wire, small, x2
#61130007446 - wire, large
#61318361787--BMW temp switch turns on at 180° and 195°
#61311378073--BMW temp switch turns on at 195° and 210°

I purchased the fans, switch, and connector through Amazon.

Fans (2): Adda 120mm x 25mm Case Fan 12V DC 175CFM Waterproof to IP55 Ball Bearing 2 wire (it looks like these fans are out of stock through Amazon and Ebay. I suggest going to either www.mouser.com or www.digikey.com. They are both reputable electronics vendors. Do a search for "fan", then use their search function to start narrowing it down to the voltage, dimensions, and IP (water, dust) ratings.

Switch: GAMA 232e3-b/b
Connector: Molex, 10 Circuit Connector -1 Complete Set- Wire Conn. with Pins - Molex Mini-Fit Jr (This connector requires that you crimp the wires. They're small pins, and if you don't have the proper crimping tool, you may have some problems. I happen to have a set similar to these, not perfect but they worked: IWISS Weather pack Crimper Tools for Crimping Delphi Packard Weather pack Terminals or Metri-Pack Connectors)

Edit: I forgot to mention that because the BMW connector comes off the thermostat at a 90 degree angle, you may need to index the thermostat so that the wires point inward towards the motor. If you don't, they might extend past the outside edge of the radiator and you don't want that. I bought a pack of copper and aluminum oil drain plug washers from autozone and they worked perfectly.

Many of these RFS motors are getting long in the tooth now, so I don't know if anyone out there wants or needs this information. If you do, and want more details, just let me know.
 
Last edited:
Joined
Oct 14, 2014
Messages
237
Location
San Antonio, TX
Got a new computer and forgot to transfer the pictures over. I have my big tank on now but will take some pictures when I change it back to a smaller one later this week.


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Joined
Jan 25, 2005
Messages
2,802
Location
Cypress Tx
I put a coolant recovery bottle on mine and cured the problum but I only rode it in cooler weather than a rode a 450 Beta , problum solved . The KTM went to a new home . I think the fan may have come on 2 or 3 times since I bought the Beta in 2013 , it is so much more civilized and requires half the effort and rider input as the KTM did . Makes cross country riding enjoyable again .
 
Joined
Oct 9, 2007
Messages
11,229
Location
Far East DFW
Interesting, I'd have been worried about the longevity of the fan as that's obviously a harsher environment than it was ever designed for but sounds like it's working good for you. A fan is on my list of shopping items for my DRZ in the near future.
 
Joined
Oct 14, 2014
Messages
237
Location
San Antonio, TX
Interesting, I'd have been worried about the longevity of the fan as that's obviously a harsher environment than it was ever designed for but sounds like it's working good for you. A fan is on my list of shopping items for my DRZ in the near future.


Prior to finding these fans, I’d went the regular computer fan route that many others have tried. None of them were durable and they never lasted. Blades would shatter or they’d just stop running. They were cheap to replace but that doesn’t help when they break in the middle of a ride.

These fans just seem to be much more durable and each of them pushes just a little less CFM than the commercially available fans. Even both of them running draws much less amperage than the commercial fans. Since they only run when actually needed, they run less than manual control plus, the redundancy of two fans means that if/when one does finally crap out, there’s still another fan left to allow the ride to continue.


Sent from my iPhone using Tapatalk
 
Joined
Oct 14, 2014
Messages
237
Location
San Antonio, TX
I put a coolant recovery bottle on mine and cured the problum but I only rode it in cooler weather than a rode a 450 Beta , problum solved . The KTM went to a new home . I think the fan may have come on 2 or 3 times since I bought the Beta in 2013 , it is so much more civilized and requires half the effort and rider input as the KTM did . Makes cross country riding enjoyable again .
I hear ya, but ~$50-60 bucks vs +$10,000 doesn't really land your solution and mine into the same conversation now, does it? My new truck with windows that roll up and down with a push of a button, air conditioning that blows colder than I can stand, awesome sound system, comfortable seats, and so on, is even more civilized than a Beta...
 
Joined
Apr 13, 2008
Messages
232
Location
Kerrville
Thank you. I've only had my 06 450exc give me problems once, but I'd rather avoid it again.

I'll be looking at doing this mod in the future.
 
Joined
Oct 14, 2014
Messages
237
Location
San Antonio, TX
Thank you. I've only had my 06 450exc give me problems once, but I'd rather avoid it again.

I'll be looking at doing this mod in the future.
You're not too far from me so if and when you decide to do it, let me know. I'll see if I can lend a hand. Or drink a beer and watch you do it.
 
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