While trail riding at the dunes my wifes 2000 300ex gets very hot on the lower part of the motor. I noticed on the right side of the motor a little bit of oil leaks out onto the frame when it gets hot. It is stock except for a K&N filter and outerware.
Thanks

 

A K&N usually requires you to jet up,any where from 1 to 3 sizes depending on how restrictive the old set up was. You are running hotter because you are lean,try 2 sizes bigger,see if it runs clean on the top end,if it sputters,go down a size. The oil leak I'm not sure of,maybe the hotter temp fried a seal,or it is just a bad seal,no way to be sure without seeing it. Hope this is some help.

 

Four Stroke Tech sells an oil cooler for your EX. www.fourstroketech.com You don't HAVE to have this but it increases your oil capacity, lengthens your oil life, and makes your engine run cooler. To me it was worth it because I have a built engine. But if my quad was stock I'd still run one.

 

Definately get the oil cooler.

 

Sice its a 4 stroke if the oil leak is coming from the head its an air leak. It will make your motor run lean & hot.

 

I disagree with MrP. Don't get the oil cooler until you fix the problem. Installing the oil cooler would be just a bandaid fix to cover up what is causing it to run hot. As 95wolv said, sounds like you need to rejet to compensate for the increased air flow due to the K&N filter.