I love riding at the dunes but as we all know our little air cooled 400's can only run great till the heat sets in. Mine is a 426 11:1 with a cam and mild port job. It runs great for about 6 passes and gets warm then falls on it's face so...

I have seen the kits made for around 100 bucks. Great deal for some but I know it can be done a lot cheaper. For $31 and some change I went to the local autoparts store and ordered the smallest tranny/oil cooler I could get. It comes with hose and clamps and the black zip binders for mounting the cooler. This one measures 12"x5.5"x.75". It has 3/8" fittings but used 5/16" hose and you'll see why.

The mounts were the tricky part BUT simple. The upper mount is made with three strips of aluminum, two are bent to a roughly 70 degree angle for the horizontal strip to rivet across where the cooler will mount. They bolt directly to the frame where the two black wire harness clips clip into. Remove them and they expose roughly 1/4" holes to bolt the upper mount to. The bottom is another strip bent to contour the cooler and bolted to the cross piece behind the bumper. I opted to use a felt weather stripping between the mounts and cooler for vibration wear purposes. The kit comes with little foam squares that serve the same purpose.

Once the cooler is mounted, it's time to adapt the oil line system. I disconnected the factory oil line on the right side (oil pressure line from engine) and cut just before the first bend with a small pipe cutter specifically to keep metal chips/shavings out of the system and for a clean cut. Then you'll take the other piece cut off and cut this about 1/4th of the bend from the factory cooler mount. The mount is reinstalled upsidedown so that it bends upward. Because the diameter of these factory lines are smaller than 3/8", I used 5/16" hose that fits very snuggly over. From the engine to the cooler and from the cooler back to the factory cooler and tighten with hose clamps. I started it up and topped off the oil with about an extra 1/8th of a quart.

Thinking mount ideas...


Mounted with the aluminum bracket bolted to the clip holes in the shock cross frame.


Plumbed into the factory oil system. No drilling, taping or any other BS required.


Fit and finished!

Thats a great idea, I think ill give it a shot

very good idea i bet there is gonna be alot of ppl that do this after they see this

orrrrrrrrrrr........sell it and get a 450. haha just joking, great idea!

Have one already. I almost like riding my lil 400 more. I'm putting an oil temp gauge on it soon to see what temperature it runs. It made a huge difference in power. I'm considering putting a bolt on kit together and I've started making the bracketry.

After looking at the pics, I think that an aftermarket hood or some creative sawzall art in the stock hood would make even more of a difference. It appears that almost half of it is behind the plastic. Granted, air travels everywhere but an aftermarket hood with a scoop and some creative ducting would make a "Ram Air Cooling" system.

Either way, it's still bad a$$!

Thanks! I kinda enjoy the factory look on it. Plus its a great sleeper. It hauls butt and is way fun to race on. I'll have to get some vids up. I have a couple racing a piped ltr450 and 450r. It seems to hold its own. It pretty much runs side by side with an HRC 450 which is right where I want it.

could you do this to a 450?.. if you could that would be a good idea for endiro. races

this prolly works great but the fourstroke tech kit has drilling and tapping for a reason. i have one on my big bore stroker motor with a good size cam and have never had the rockers hardfaced, with the oil being picked up before it travels up the cylinder then out to the cooler, then directly into the end of the cam. that is the purpose it is supposed to serve with the kits. yours is effective, just in a little diff way. looks like a clean install also! i know just like you do, anything you can do to keep the little 400ex cooler makes it perform alot better

chris

Very important for the heat. Really become as a handy thing for the bike.