Just be ready for fluids to come out. Make sure to flush all that gunk out of the cooling system. You can put some degreaser and water, or soap and water, in it and let it sit for a while to break up the oil, then run water through it before adding coolant to it.

 

Same problem happened to me a few years ago and the oil cooler I completely agree and is less time consuming/ money wise to fix. Replace all the O-rings/rubber gaskets on the oil cooler. I spent maybe $16 and fixed the problem. They get hard and crusty after 20 years. If that doesn't fix the problem then it is your head gasket.
My clutch started slipping all of a sudden and a funky antifreeze/burning oil smell rose and that is when I checked the coffee colored oil and knew something was wrong. Luckily someone on this forum told me to check the oil cooler first and they were right.

 

You guys all couldn't be more right! I'm truly thankful that we have such a helpful forum. It did turn out to be the o rings in the oil cooler. The water pump seal has been replaced just to be sure. The O-rings in the oil cooler were completely warped and they were literally falling apart. It's no wonder I started getting oily muck on the bottom of my radiator cap just 2 months ago. I took the trouble to take pictures despite my super dirty hands hehe. I hope these pics will help future people with the same problem. I'm glad I bought a universal O-ring set last year for $15 bucks. The cost at the dealer for 2 O-rings was ridiculous! Anyways, thanks for everyone's help! I hope to last another 50k miles

 

those images need to be stickied or something.

 

I Second this need to be a sticky!

Our bikes are getting older and I can see this question coming up more for this easy fix.

 

Sorry about that! Here you go: