I'm thinking you're OK unless the motor is making expensive noises. Here's what I'd do.... drain old oil and change filter (presuming you've done that already). Fresh oil and filter and run the bike for about 25 miles to warm it up thoroughly. Add a little MMO or your preferred engine oil flush in the recommended dose and run for a few more miles, drain oil and put in new oil and new filter again. If there's any bad stuff in that treated oil you drain out, you might want to worry. If not I'd say you're golden. Then do a compression check and check your plugs. If everything's within normals, get on it and ride. Change your oil and filter again in 3000-3500 miles just to be sure. These engines are tough and will tolerate a lot. We probably baby them more than necessary. I wouldn't do an engine rebuild unless you start making expensive engine noises or notice a real significant loss of power.
John Scribner