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Old 05-09-2005, 07:49 AM   #32
Adventure Antagonist
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Joined: May 2003
Location: Las Vegas, NV
Oddometer: 1,164
Mounting a right-side fan on a 640 Adventure

With summer quickly approaching, I figured it was time to mount a right side fan. Besides, I sent my seat back to Bill Mayer for some adjustments, so I had some down time to play. Through prior experimentation with the left-side fan, I knew I could get it in/on. It was just a matter of making some brackets and relocating the condenser. Then I’d run some wiring, mount a switch and I’d be set.

It really wasn’t that bad. Most of the time was spent creating & bending the brackets for the fan and the condenser. Here’s the Reader’s Digest version of the install:

1. Relocate the condenser. Luckily, KTM realized I’d be doing this and included this wonderful mounting lug at the right rear of the head. You can see it just below and behind the green temperature switch. I just used a little “L” bracket to go from the lug to the condenser mount. Wires are long enough and there’s enough clearance to get an allen wrench in there if needed.

This is what used to be mounted to that lug (battery for scale only):

On my bike, there was nothing running through it or attached to it. It’s just an extra part now….

2. Mount the fan. Now the fan just barely fits. The compression release arm off the exhaust valve cover touches the inside edge of the fan housing. Two of the four fan mounting holes line up ‘almost’ perfectly with the tabs on the edge of the radiator. Close enough though. So you have to fab a couple small brackets to mount up to the radiator, and at least one inboard mount. I ran the inboard fan mount from behind the rubber gas tank mount, around behind the compression release cable, then to the fan. This required a lot of twisting and bending so make sure you use something that can withstand the abuse. I used a 2” diameter flat steel pipe clamp. For the radiator brackets, I just used a couple more small “L” brackets. A little cutting/grinding of the brackets is also needed where they attach to the fan itself. Clearances are small. Use your favorite nuts/bolts/screws to secure everything. Here’s how it looks:

Here’s a wider image including relocated condenser:

3. Wire and switch. I used a DPDT, weatherproof (triple sealed) switch and wired it so I could manually override the LS fan, or turn on the RS fan. To turn on the LS fan, all you need to do is short the radiator temp sensor terminals (under the boot). So I cut off the original spade terminals and ran a pair of wires from the switch and spliced them in to the existing (brown) temp sensor wires with new spade connectors. Now, when I throw the switch, all I’m doing is closing the connection at the temp sensor and the LS fan kicks on. This has no effect on the automatic operation of the fan. If I have the switch in the OFF or RS fan position, the LS fan will still kick on automatically. For the RS fan, I wired it direct from the battery with an inline fuse. I thought about using a relay, but the fan really doesn’t pull very many amps, so I decided to do without. Anyway, the RS fan is wired so that throwing the switch just completes the ground and it fires right up. One benefit I noticed is that since it’s running direct from the battery, it spins at a higher RPM.

The switch (above & below the dash):

Switch wiring close up:

4. So, with the switch in the central (OFF) position, everything works like normal. If I toggle up, the LF fan fires up and if I toggle down the RS fan comes on.

I haven’t been able to road test it yet as my seat is still at Bill Mayer being “adjusted”.

Some notes: The clearances are very slim. The fan is only millimeters away from the radiator fins. When the tank is on, there are only millimeters of space between the inside of the tank to the fan mounting brackets. I made sure to cut off any extra bolt threads so they are flush with the heads of the nuts. Also, as an aid for working on the bike, I made the connections to the RS fan using posi-locks. I also made the wires to the switch extra long so there is some play when I pull the dash.

Kinda looking forward to summer now. I used to stress every time I’d get stuck in traffic on the way home from work as the temp gauge would creep up and up. I knew the dreaded yellow blinking temp light wasn’t far behind. Sitting on the side of the freeway when it’s 100+ degrees while waiting for the bike to cool down is not my idea of a good time. Shouldn’t have to worry about that anymore…..
Currently bikeless.
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