Would a 2002 Honda rebel 250 be to small for me?

I'm 6"6 and 375lbs

Every motorcycle has a little different 'ergonomics', the spatial relationship between the seat, handlebars, and footpegs. How it 'fits' you is entirely subjective. Nobody can tell you. The only way really to tell is to find one and sit on it and see what you think.

I think you will feel cramped on a Rebel, but wtf do I know? It's how YOU feel that's important.

Also the Rebel, being a 250, is not really capable of cruising at highway speeds. Your weight is not a problem for the bike to carry, but at sustained speeds above about 50 mph the bikes' going to be beating its little brains out.

I think it will make you feel like you are riding a child's toy trike. Can you ride it? Sure. It will give you a great first experience on something that is hard to harm if you make mistakes. Sit on one, see if you don't feel cramped. I'm a foot shorter than you and I felt like my knees were in my lap.

You'd be better off with something like a Suzuki GS500. Maybe even a Kawasaki KLR650, as you're 6ft6.

Around town you should be ok but freeway may be an issue. The big problem is the bike frame the rebel is designed for people with about a 30" inseam you being taller and longer legs might feel cramped on a smaller bike. Personally I think looking into the Shadow may be a better option. Go ride the Rebel you'll know in about 5 miles if it is to small…

I think you'd be fine.