You know, I was in Rio four times on business in about 1997. I loved it. It's an amazing city for topography, beauty and culture. And Junior is right - I'm sure some of the riding would be amazing. (And about the women there. I saw very few "10's" but tons of "6-7's". Pretty girls are everywhere, especially if you're partial to exotic, Coke-bottle-shaped women.)
But I will almost certainly never go again - especially with wife & kids, or even without them along. The city has too much potential for danger.
Especially if you're a Caucasian, I wouldn't spend much time outside of the relatively "protected" areas of town, especially on a motorcycle. While I was there, I personally had nothing unfortunate happen. Every other American I know, though, had something go wrong: being robbed at knife-point on Ipanema Beach in broad daylight; having a band of thieves - like 40 of them - "sweep" the beach for 100 yards straight taking every single thing of value; having girls pick a guy up, take him to a "friendly" bar to get him to buy them drinks, and recognizing it to be a scam where he's actually bought everyone in the bar drinks - for like $1,000; someone having everything in their hotel room ripped off - in a nice hotel; etc. Not to mention the kidnappings, killings, that one hears of, etc.
You may suspect that I'm simply some wimpy, unadventurous American, but you'd be wrong. I've traveled to 35 countries, more than 600 cities around the world, including Mexico City many times and other dangerous places, and I've never felt the kind of impending danger that I have in Brasil, after going down there with a very open mind. I loved the place and drank and partied all night on occasion with local colleagues. But the whole scene is still super sketchy. I'm 6'4", 240. That doesn't help with faced with a band of teenagers or worse, with or without weapons.
Besides all that, people drive like idiots and the traffic can be maddening.
For some reference, watch a couple of movies that you may enjoy: City of God, City of Men or Elite Squad - all life-based films about the "favelas" outside of Rio.
Be careful. And let me know if you enjoy riding there and if I've been completely wrong.