State laws and insurance companies' guidelines differ regarding when a car or motorcycle is determined a total loss. In general when repair costs exceed 50 to 75 percent (or more) of the vehicle's actual cash value (ACV) and insurer will normally total out a vehicle. Each insurance company has their own way of calculating ACV but typically it can include the blue book or NADA value, local comparable vehicle sales and their own internal information.
If there is major structural damage to a vehicle that cannot be properly repaired or that makes it uneconomical to repair the vehicle then it typically is declared a total loss by an insurance provider. If a scraped frame on a motorcycle means that the frame had to be replaced or go through extensive and expensive repairs then it may cause the motorcycle to be totaled out since it could be uneconomical for the insurance company involved to fix the bike.
If your motorcycle has been in an accident that damaged the frame (scraped, dented, etc) then speak with the insurance adjuster working the claim to find out how the company determines when a vehicle is totaled out. You can also ask if according to their specific guidelines there are certain damages such as frame damage that automatically causes the insurer to find the vehicle a total loss.
As for state laws regulating when a vehicle should be totaled out by an insurance company and be found to be a salvage vehicle, contact your state's insurance regulatory body for consumer advice on this subject. They can give you information on your specific state's laws.