Who's installed a fan on the radiator?

.. seen lots of threads where it's suggested and a link to the RMZ forum where a guy put one on his 450. Just looking for real-world experience on our bike (I have a '99 YZ400F)..

I can figure out a good fan, where to mount a battery, etc. but would like to see what others have done so I could learn from their misteaks first! :smirk:

Riding with my family, the YZ is losing a LOT of coolant, need to remedy this before the next time out.

Also, how many have installed coolant recovery/overflow systems? I caught this post in the same thread: http://www.thumpertalk.com/forum/showpost.php?p=668915&postcount=4


Studying the fiche, looks like the radiators are parallel, so is putting a single fan on one side effective?


A single fan is much more effective than no fan, yes. But you should also check the basic stuff. The YZ400 had smallish radiators. Those on the 426 are somewhat larger, and the WR426 radiators are larger yet, and I'm pretty sure they bolt on.

Check your pressure cap to make sure it's holding the rated 16 psi (most shops should be able to do this) and be certain the radiators are clean internally and externally. You might also want to bump the coolant mix to 60 percent.

Thx. As many have stated, if there's no air moving, the size of the radiators doesn't help. I'm having to stop and wait a lot, as well as ride slowly for the bulk of the time. I'm shutting the bike down if it's going to be a minute or two before they catch up, and that's a bit of a pain as well. :smirk: I know this isn't the bike for that kind of riding but it's what I've got for now, and I have no problem when I'm on a trail by myself or riding with more experienced folks.

I've ordered two beefy PC fans that push >110cfm, and will put one on each side. Just looking for mounting ideas from those that had done it before.

I've also got a small thermometer with a remote probe, I'm going to attach it to the radiator with high temp silicone or something, and see what temps I get riding around the house, before and after the fans.

I'll also do the overflow thing to help keep fluid in the system, but I want to prevent the boiling if possible. When you say "bump up to 60" do you mean add more water than coolant?


No, more coolant than water. That will raise the boiling point, but the downside is that the water part cools more effectively than the coolant does, so there are diminishing returns by exceeding 50/50.

Another thing that can help a little is switching from ethylene glycol to propylene glycol coolants (small edge on boiling) and add a little bit of surfactant, such as "Water Wetter" by Redline. This is more improtant when using straight water than when using coolant, but the idea is to help form a better thermal connection between the metals and the water by breaking the film tension of the water.

On most bikes, you could go to a radiator cap with a higher pressure rating but in your case I would avoid that. The OEM Yamaha radiators on older YZ's and WR's are very weak at the tank seam and where the outside brace is brazed to the side of the tank. Add to the mix the fact you have radiators that are 13 years old and you could split a seam with a 22 psi cap.

Make sure your radiators are clean on the outside where the fins and tubes are. Don't use a pressure washer. Use some Simple Green and a garden hose to glean the outside of your radiators.

Also make sure that the fins aren't flattened and blocking airflow. If they are, you can use a toothpick or something similar to straighten them out.

Radiators are in good shape, and clean. Whole bike is for it's age, actually. I'm using the orange prestone (dextron?) as that's what I use in my street bikes. I can add some water wetter.

Again, the issue here is that I am *very* slow a lot of the time when riding with them - we're talking idle in first gear speed here - or even stationary waiting on them. I hope the fans will do the trick and the overflow will ensure the system stays topped up.


Are you doing slow stuff up steep hills? You shouldn't be having boil-over problems even if you are going very slow as long as the engine is under light load. Deep sand and long, slow, steep hills can make any bike overheat if you are heavy into the throttle.

I thought of the same things... My plan was to put a battery in the airfilter box, some fans, and attach a sensor with an adapter like this:


I have plenty of batteries - rechargeable lithium high capacity. I could run the fans I bought for more than 24hrs on a <1lb battery. This may be a temporary solution until they get more comfortable on the bikes, or we find a series of trails where we can ride at a decent speed. It's only the hard stuff that slows them down..

Hey Rasmus - where did you find that sensor adapter??


I'll keep that in mind if I go with an temp-controlled circuit.. thx!


I'm interested in this too for my 05 YZ450F.

Why not use a power out stator... http://www.ebay.com.au/itm/New-4-Pole-Lighting-Stator-35W-Yamaha-YZ250F-01-09-YZ400-YZ426-450-03-05-ESL380-/290617362398?pt=Motorcycles_Parts_Accessories&hash=item43aa2507de

Then you just need to work out mounting, and a sensor / relay setup...

If you add a lighting coil you will need to convert the output to DC if you are going to run any fans. You could avoid the DC conversion if you could find a 12v fan motor that doesn't use permanent magnets and has a brushed armature (unlikely).

If you are going to use a lighting coil and a DC conversion the lighting coil has to have a floating ground.

At this point, I know of absolutely no reliable aftermarket stators for any non-EFI YZ450 that include lighting/auxiliary power coils. The only exceptions are the old E-Line external stators for the '03-'05 models, and they aren't made any more. None of them hold up well at all.

At this point, I know of absolutely no reliable aftermarket stators for any non-EFI YZ450 that include lighting/auxiliary power coils. The only exceptions are the old E-Line external stators for the '03-'05 models, and they aren't made any more. None of them hold up well at all.

You could wind your own. Pick up a used one and give it a shot.

There is a guy that lives not far from me that had a pretty successful business rewinding stators out of his garage, unfortunately, after the flood of cheap chinese aftermarket stators about 8 years ago, his business fell apart. I did learn some tricks for winding stators that can withstand some serious abuse. For a while he was supplying Johnny Campbell's race team with stators for his Baja bikes. The first thing they would do with the stock Honda stator is toss it in the trash, then they would one of Carl's rewound stators. Never had one fail in a race.

From conversations I've had with a couple manufacturers in SoCal, the YZ450F stator is simply too small to be able to reliably produce the current needed to run the engine at half its coil size. Even then, it can barely produce 35w of DC on the half that got stolen for lights. The whole thing ends up having to run at full capacity full time, and just can't cut it.

For those who haven't looked at one here's what I mean when I say the thing is too small to start with:


Well, a little more research before I ordered the fans wouldn't have hurt (I can always use them in a PC)..

There is NO room whatsoever between the tank and the right-side radiator - there's about 1cm of clearance. The other side is more open but the pipes are running along the radiator and it wouldn't be a good place to try and squeeze in the fan.

Obviously they can't go on the front, too exposed..

So I've got another idea, that's to find a set of old plastics and mount the fans to those, blowing 'out', so that the air is kind of drawn through that area.


Ok! I was sure there could easy be a PC fan in there on mine, I dont have it here at home right no so cant check.. not that it matters much :smirk: maybe its that safari tank you got there...

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