Adding cooling fans to a 06 yz450

[700rScott]

I have my bike set up for trails and soon to be super moto, I'm going to be adding fans ran off a battery but I'm trying to figure out do I need 1 or 2 fans to keep the bike happy on single track trails or sitting at a red light. This summer I've seen it get up to 250 degrees on a trail before I was able to shut her down for a few minutes to cool her back down. The fans I'm looking to put on are 4" spal fans that pull 147 CFM so I don't know if I can get away with just the one or do I need two. Thanks

[FORMA MOTO]

For fans that size/cfm you will need two, especially if you are not using a shroud. 

If you use a shroud, the fans have to run 100% of the time.

 

You really need to make sure the cooling system is 100% before bothering with fans.

Flush the radiators or have them rebuild tby Mylers, put in quality silicone hoses, raise you cap to 1.3 or 1.6, put in modern coolant, and add a recovery tank so you don't get stranded with low coolant.

Edited September 18, 2015 by KRANNIE

[Gunner354]

For fans that size/cfm you will need two, especially if you are not using a shroud.

If you use a shroud, the fans have to run 100% of the time.

You really need to make sure the cooling system is 100% before bothering with fans.

Flush the radiators or have them rebuild tby Mylers, put in quality silicone hoses, raise you cap to 1.3 or 1.6, put in modern coolant, and add a recovery tank so you don't get stranded with low coolant.

Install Evans coolant and you won't need a recovery tank or different cap. It boils at 375* with zero pressure

[grayracer513]

To start with, when using conventional propylene glycol coolant at 50/50 and a good stock 1.1 bar cap, temps of 250 ℉ fairly high, but well below boiling, and are safe.  When it hits 265 ℉, that's the red line.  

 

Stuff like Evans boils at about 425 ℉, and even when not boiling, 400 ℉ coolant temps are not particularly safe at all.  The only reason you should use it is for extreme cases where temps in that range would be unavoidable, and coolant retention becomes a more important consideration than temperature. 

 

For an SM bike, I imagine that your concern is with traffic and stop lights.  Two 3-4" DC fans built for computer chassis and such are all you need, and they can be mounted directly behind the radiators without shrouds.  You can rig a temp switch, or just a manual toggle, and you can power them for a good couple of hours off just a pair of 9v batteries if it comes to that. 

 

Silicon hoses are blingy and cool, but they have no particular practical advantage over OEM, or bulk standard coolant hoses. 

[700rScott]

I'm planning on putting in a boysesen high flow pump and changing the coolant to liquid ice. I do have a over flow tank to catch any boil over and have not had an issue with it yet. I was looking at the spal fans so they can take the dirt and water for offroad cause if it was just a street machine I know the computer fans would be good enough. The spals drawl 2.2 amps so I'm looking at the antigravity 4 or 8 cell battery to power the fans, the head light (but that will be rarely used) and the LED turn signals/ tail light. I have a 3.5 amp hour trail tech battery now powering the lights, I'm going to try to hook up the HD stator and hope for the best it lasts so I can charge the battery when it's not on the battery tender at home. I don't have much room to add a shroud due to the rad guards so the fans will just be mounted down towards to bottom of the rads. The controls of the fans I was planning on putting an on off switch to over ride a automatic in line temp sensor so I can shut them down if they're running too long and just shut the bike down to cool it down naturally. I don't want to go too crazy with the pump, coolant, oversized rads, smooth tubes since she'll run about 160-170 when cruising at speed so I don't want to get much below that when I'm on the roads.

Edited September 18, 2015 by 700rScott

[grayracer513]

Bear in mind that fans are generally ineffective at speeds above not much more than 10-15 MPH.   Their only real purpose is to maintain air flow over the radiators when there is none otherwise. 

[700rScott]

I can keep the temp down usually anything to mid rpm in 2nd so it's just that real slow stuff or at a stop that I want to help out. Riding with two smokes on the trails doesn't help with keeping the temp in a normal range and I have a 300 on the wish list to get but until then I have this monster to ride so anything to help tame the beast is better than nothing.

[mike_dean]

The trail tech and ktm cooling fan are great and come with everything you need. My ktm has one and is a life saver on a 4 stroke in an enduro in the midwest. My smr510 husky overheats in traffic, thats my next purchase.

[700rScott]

The trail tech and ktm cooling fan are great and come with everything you need. My ktm has one and is a life saver on a 4 stroke in an enduro in the midwest. My smr510 husky overheats in traffic, thats my next purchase.

I've looked at those and I don't have room for them there so I have to squeeze them in at the bottom. I found these fans so I'm undecided between them and the spals.

http://www.amazon.com/dp/B00AJO2C2Q/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=1699GKON9AY0G&coliid=I14AFK0EI6PP2I

This what I'm working with cause the WR tank doesn't leave a whole lot of room between the tank and rads. I had a IMS tank on too and it was almost the same situation with the spacing.

[mike_dean]

I've looked at those and I don't have room for them there so I have to squeeze them in at the bottom. I found these fans so I'm undecided between them and the spals.

http://www.amazon.com/dp/B00AJO2C2Q/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=1699GKON9AY0G&coliid=I14AFK0EI6PP2I

This what I'm working with cause the WR tank doesn't leave a whole lot of room between the tank and rads. I had a IMS tank on too and it was almost the same situation with the spacing.

Wow that is tight.

[700rScott]

Wow that is tight.

Yeah, tell me about it. I'm not sure if I can squeeze part of the spal between the rad and tank.