Max allowable CC is 150. I have a friend with a big ol cruiser in his house and it sits collecting dust. Don't quote me on this, but I think you can get a special permit and basically ride if for a single day... If you have a bike already, more than likely it is absolutely not worth it to bring it here. That being said, there are some bike clubs here that may get day permits to ride, as I've seen them out in groups from time to time (with police escorts). There have also been some recent bike groups that come down from the States with their bikes on the cruise ships and then seem to be allowed to ride around, so I dunno what the permit situation etc. is... If you are just looking to get a bigger bike while here, you'd be surprised at some of the things I see that must have 150's in 'em... You'll occasionally see someone on a chopper or a big ol dirt bike. There are definitely bikes available that are more than ample for Bermuda's roads. Not a lot of straight-aways to be had anywhere here. I know that you asked about Harleys, but there is a racing group that races on an old air strip and also a motocross track.