Was thinking about adding a oil cooler to my xt 550 dirtbike as this bike runs pretty hot. How hard would this be to do? Would a four wheeler cooler work on my bike?

Are there oil lines already?

I'd think that Yam made the bike without one, and it's ran fine for YEARS with out one so why bother?

Unless you've upped the comp or somthing silly like that, the motor dosnt really get "that" hot

No I don't need one I just thought it would be a cool little mod. Your right it doesn't come with one and its got oil lines on it since it's a dry sump system. I was just wondering if it was worth the money and how much it would cool the motor down to get some power back when its hot.

If you're serious get hold of Mickey Dunlap at Four Stroke Tech in NY State. He has a cool kit which hooks into the oil gallery on the right side cover and has a small oil cooler that won't get in the way.
I fitted one to a Warrior I had, it was pretty easy and worked well.
But I only got peace of mind, didn't notice any more power. The power came from an FMF muffler and Pro Design air filter system. With all the mods it felt like a 500.
But having said all that, the Big Bear oil cooler fits over the oil filter setup which is the same on most yammy 4strokes.
But boy would that be bulky.
Besides having a dry sump with the frame reservoir is similar to an oil cooler anyway.
I have a TTR 250 and just change the oil with good semi synthetic 10w-40 every 2 to 3 trail rides, depending on how hard and long the rides are.
Alfie.

The XR400 has an oil cooler. Check the microfiche at Troy Racing.

I not to serious just a idea I was thinking about. Maybe A guy could weld some cooling fins on the resveroir. It would kind of look dumb and take some time but I think that would help. Thanks xr400 for letting me know that. One think about engine running hot is the oil doesn't last to long. I change my oil a lot more often than any of my friends but around every 3 or 4 rides may be too often. I like to change mine just when it start turing blacking and getting thinner.