So I'm going to be buying my first quad here real soon, a 400ex, and I'm going to be going all OCD on the cooling system because I live in the desert of the South West, specifically Las Cruces, NM where the temperatures are regularly in the high 90's low 100's during the summer... I have a few question though.

I'm going to be installing a Spal 4" puller fan behind the oil cooler, which will I would like to have toggled off and on via a temperature switch inline on one of the oil feed lines. My question is, what is the ideal operating oil temperature for the 400ex or a 4 stroke in general, and where should the temperature be measured, on the oil feed line from the engine to the cooler or on the feed line from the cooler to the oil tank? I would assume on the line from the engine to the cooler would give the most accurate reading, but so far in all my research everyone seems to talk about oil temperature measured in the oil tank via a dipstick temperature gauge.

I'm also going to be running a cooler spark plug and Mobile 1 full synthetic 15w50 or 20w50 depending on ambient air temperature. I'm thinking I'll run the 15w50 during the spring and fall when temperatures are usually in the 60-80 degree range and the 20w50 in the summer when temperatures are in the 80-100+ degree range.

All that should be good enough for cooling, BUT if I still feel I need more after that I will be installing a 2nd oil cooler.

 

Everyone talks about the oil temp at the tank because that is the only place you can get a reading without some expensive tools.
If the t-stat is pre cooler one would assume that the fan would be running more than if located in the return line. Personally I would locate the t-stat in the return line. Logic, let the cooler do its thing first and if it cant keep up then the fan kicks on.
I have a spal fan on my ex to-do list. When I get around to do it my fan will just be on a toggle switch. I think the less connections you have the safer you are. With that train of thought I would also look into a larger oil cooler rather than 2 coolers.
There is also something to be said for a larger oil tank and air scoops. The larger tank and scoops wont help a tremendous amount on their own. But when you look at it as a whole unit/system I feel the gains would be solid with the 4 mods.
Last but not least jetting is KEY to keeping these air cooled machines running cool.
Hope this helps, best of luck!!!

 

Thanks for the reply! I'll definitely be setting up the jets correctly. As far as the temperature switch, I want to run one of these:



Its a simple thermal switch with a 180 degree on and 170 degree off. It would get wired to the ground connection on the fan. Placing this on the return line would probably be best for the reasons you stated.



As for the oil cooler, I was actually thinking of running a 2nd larger cooler along with the stock cooler, not two stock size coolers. Maybe thats overkill? I know you don't want the oil to get cooled too much either as that could also harm the engine... Something like this:



which I found on this thread: 400EX Extra Oil Cooler Install - Honda TRX Forums: Honda TRX 450R Forum

 

Looks like you have a pretty good plan for keeping your ex cool . Most of the additional oil coolers on a ex are just aftermarket tranny coolers for light duty trucks.
Seeing how you are in the desert a second cooler in the very front of the machine should work rather nice. With a setup like that a good front bumper would protect the cooler rather nice.
Have you looked into a secondary oil cooler from FST? The return line is tapped into the rocker cover.
Welcome to 4 Stroke Tech, Inc.
BTW there is no such thing as over kill.

 

I'll look into that cooler kit for them. Thanks! The oil cooler in the picture I posted was from another thread, the guy said he just went to the local auto part store and ordered the smallest oil/tranny cooler he could find, only ended up costing him a little over $30!

 

Its hard to beat a cooling setup for under $50. I dont remember the dimensions but B&M makes a tranny cooler that is the same with as the stock ex oil cooler but its taller. So one could replace the stock oil cooler with a bigger unit instead of running 2 coolers.
Hope some of this info helps ya. Sure would like some pics. of your finished product!

 

Everyone talks about the oil temp at the tank because that is the only place you can get a reading without some expensive tools.

 

The second oil cooler mod works to a point. If your not putting the cool oil back into the head where its needed then its really not doing a good job. you need to divert the second coolers oil return to the top of the head.
You can buy the kit from Four Stroke Tech which is a quality kit but they have cheaper kits out there on ebay. I have the instructions on how to do it properly.
This is good for about 40*-50*. I live in Alabama and I have a 500cc 400EX with only the oil cooler mod and oil temp never exceeds 260*. Rotella T 15w40 diesel oil is what I run and is good up to 300* as per Shell Oil.

 

I am known for going OCD on cooling too. Everything I build/work on has to have extra cooling. For one I am a bigger guy, two everything I run gets rode hard! I will try all kinds of things that should never work or be done.

I am doing the FST cooler on mine but with a bigger cooler than the one in their kit. Autozone sells the cooler in your picture for about $30, then you can get the 90 degree barb fittings from Summit to do a nice clean install.

After all that I am probably going to also run a fan but a 6" on the FST cooler not the stock one. Personally I like the temp switch route so you don't have to worry about knowing if it should be on or not. It just kicks on when it needs to and shuts off when it needs to. No guess work.

And I did get the XRS dip stick. What good is all the extra work if you don't know if it works or not? I put in the dip stick and am going to take it for a short trail ride and see how hot it gets, then going to do the FST cooler and see how much it helps.