Jump to content

DIY KTM Radiator Fans


GasitandCrash

After experiencing some overheating while going slow in rough terrain I decided to try a cheap fix and install a couple of cooling fans. Here are some photos of my fan installation.

 

The fans are not sealed but since they are brush-less DC fans, unless some debris gets in them they should not be affected by the environment. The fans are fairly inexpensive draw very little current and easy to replace if they fail. The fans are held on the radiator by zip ties. I inserted one zip tie through each of the radiator side mounting holes of the fan then passed the zip ties through the fins if the radiator and secured them with the clipped-off head of another zip tie.

 

The 2006 250 xc-w does not appear to have a 12vdc circuit. It does have an output from the generator that I assume is alternating current. Since the stock regulator only has one wire going to it and ground on the other side I suspect is just a zener diode, that acts as a voltage limiter shunting anything over a certain voltage to ground. If that is the case the AC generator output would be fine for lights and a horn, but not a Direct Current Fan. I installed a inexpensive (cheap) aftermarket regulator/rectifier, inserting it between the generator and the rest of the KTM's electrical circuit. You can see the voltage regulator in the attached photos. The regulator/rectifier provides 12vdc to the fans, horn, lights and the battery.

 

The battery pack is a ni-mh 1800 mha 12vdc, NOT lithium-ion. I opted for the ni-mh because there is less of a fire hazard in-case the voltage regulator goes nuts. The battery is connected to the rest of the circuit with a 7.5 amp fuse and is intended to act as a voltage conditioner. If the voltage provided by the regulator has any rpm related spikes, or dips, the battery should absorb the spikes by charging, and fill any dips by discharging. Or at least that's the plan. The battery also powers the fans if the radiators are still hot when the engine is not running.

 

The fans are activated by an appliance thermo-snap switch. This switch is a normally open bi-metal switch that closes at 85c (185f). It is designed to switch 120vac at 8 amps. That is an order of magnitude more current then the fans require, so they are not likely to fail due to current draw. If it fails it will probably be a result of exceeding the cycle life of the switch and I have NO idea of how many cycles to failure this switch is rated for. It is attached to the radiator just below the radiator cap near the hot coolant in hose using JB weld epoxy adhesive. The switch activates after the stock thermostat opens fully and the coolant temp at the top of the radiator exceeds 85c.

 

Since installing the fans, a coolant recovery bottle and a 1.8 bar radiator cap, even though I have been riding harder, I have not experienced any steam from overheating. I have seen the coolant recovery bottle over half full. So the cooling system with the fans running has gotten hot enough to overpressure the 1.8 bar radiator cap and over flow coolant into the recovery bottle, but it did not over flow the bottle, and all of the coolant was returned to the radiator as soon as the bike cooled. The fact that the coolant bottle did have coolant overflow in it is proof that the fans and 1.8 bar radiator cap are not a total cure to overheating. Though as I said overheating has happened far fewer times even though I'm riding more and harder than last year. The thermo-snap switch ensures that the whole system is automatic requiring no input from the rider. The fans turn on and off according to radiator temperature whether the engine is running or not. The fan system weighs less than 1 kg (2 lbs). All in all I am very satisfied with the way it works.

 

I know the wiring is a rats nest. It was pretty much a proof of concept job. My son was going to clean it up and give it a more professional look, but I haven't gotten it over to him yet (1year+)

 

>>> See my coolant recovery bottle system HERE.

 

ccs-3-0-07001200-1433862449.jpg

 

ccs-3-0-20057800-1433862470.jpg

 

ccs-3-0-94916200-1433862482.jpg

 

ccs-3-0-40090900-1433862487.jpg

 

ccs-3-0-23536200-1433862504.jpg



User Feedback

Recommended Comments

Sofasco, a company in winchester va makes all sorts of sealed harsh enviroment fans for cheap. See what the have laying around and pick your size and ctm. Great idea!

Share this comment


Link to comment
Share on other sites


Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


  • Similar Content

    • By fudgypup
      Garrett Poucher and Skyler Howes of Garrett Offroad Racing are headed to Dakar!  These US privateers are headed there for their first times but Skyler is fresh off a victory at last week's Baja Rally, won the Sonora Rally in March and this team placed third in the Baja 1000.

      They have a fundraising link set up and could use your help.
      I raced with Garrett at Baja Rally last year and then both of them at Sonora and was honored to pit with them as well.  They're both super guys and work their assess off.  I think they both have good chances of not only finishing the 11 days of Dakar but placing well.
      They're doing some rally training events this Sat, Oct 20 in Santa Clarita, CA and then another Oct 28th in St. George Utah so if you've ever considered learning rally raid navigation, this is your chance!  It's a lot of fun too.  More info on that at the link.
    • By jAcee
      I just got done rebuilding my 99 ktm 250sx and after i got done i started it up it wouldn't idle or start with out a quarter throttle and it would get up in the rpms buy would die down quicker than normal 2 strokes. it was getting gas it didn't sound like it wasn't getting gas the rpms would go down super fast i messed with the idle screw but it wouldn't do that before i had to flush it out with oil cause the piston blew apart it feels like its getting seized at a certain point of the stroke i would just like to know the reason why 
    • By Big64N
      Good condition with a long list of high end upgrade parts.
      Rekluse EXP 3.0 with cover and slave
      EVO- Ellensburg suspension tuning for 6' 200# expert rider
      Fork bleeders
      Trail-tech map switch
      Moose 1-1/8 flex bar
      CYCRA probend bar guards
      SXS skid plate with linkage plate
      Clutch and water pump guards
      Frame guards
      Fastway Evolution III pegs
      SRT Pro Armor radiator and rear rotor guards
      Acerbic Front rotor guard
      TM designs chain guides
      DID race chain
      Renthal sprockets
      Gripper seat
      FMF F-bomb header
      Dirt Tricks timing chain tensioner
      Pro Wheel, wheels
      Tubliss front and rear
      New top end and valve adjustment 60 hours old
      Many more aftermarket parts as well as spare parts and service manuals included in the sale.  Willing to include 4 sets of tires with 80% tread left for full price.
      Great bike with plenty of life left and set up for anything from single track woods to wide open dessert.
      Can hang with any of the 450's but is much easier to handle in the tight woods.
      Priced to sell at $6000.00 
      Willing to consider reasonable offers but no trades or carry.
    • By Bobby Iverson
      Was riding my 450, testing out a new speedometer, shifted into 2nd, moved a couple feet and heard a loud crack noise from engine area. Will not turn over, sounds like its jammed or seized from moving. My guess is tat the timing chain just exploded and fouled everything up. Haven't found time to open it up. Thought I'd go to forums to get some opinions on what to look at first. As far as back round info: Engine was opened up to replace some gaskets. replaced my valves and adjusted rockers to .05mm. Timing chain taken apart a couple times. Shifts through gears fine even though it doesn't run. I am not very fond of ktms or dirt bikes in general but fairly mechanically inclined. I don't know what to do so here I am on the forums. Any help or advice is much appreciated. Thank you.
×