Don't know about the following places in Udon Thani but it maybeworthwhile to contact them and ask what they have available.
Cars & motorbike hire / rentals are available from the following locations;
* Steve's Udon Beer Garden (Cars and motorbikes for rent)
Contact: Steve on 09-2765996
Website: Link removed
* Aussie Pub Udon Thani (Cars and motorbikes for rent)
Contact Justin & May: 06-1086359, 09-2527129 Website:
* Steves Bar & Restaurant , Udon Thani (Cars and motorbikes for rent)
Contact: Steve on 042-244523
I've never seen any sport bikes for rent in Isaan, but in Khon Kaen they have smaller bikes like the Phantom and Kawasaki Boss for rent. A rental place in Sofitel has one 175cc Boss and a restaurant across the street (Steak House 23) has a new 200cc Phantom. You can get both places down to 400B a day. Not the 400-600cc sport bike your friends are looking, but the closest I've personally seen in Isaan.