When you first phone up a number about the bike, introduce yourself and begin by asking open-ended questions; avoid using simplistic ‘yes’ or ‘no’ inquiries. Focus on getting answers to questions like, "can you tell me about the motorcycle?” or “are there any known issues with the bike?” Continue by asking about whether there is a solid service history, if the bike has been on a track, about the overall condition – and, if it has ever been down. The more you get them to talk about the bike, the more likely they are to mention something which could clue you in to any issues. The previous research you have done will be very helpful here; go ahead and ask the seller about those potential problem areas.
Ask the seller the price at this point. You may find that it has been reduced since the ad was placed, or the seller may simply believe you to be a serious buyer and wants to sell it quickly. If they ask what the ad says, though, be honest.
If you decide to go and take a look, ask that the bike NOT be warmed up when you arrive. You will want to see how well it cold-starts and you can examine the bike more closely when not afraid of being burned.