I was hit and injured while I had the right of way on a road by an underinsured driver. We are both insured by the same company. My motorcycle suffered damages assessed by my authorized Honda mechanic to cost $10,900 to repair.  However the repair estimate the insurance company states is $11,700.00 and declared my cycle a total loss and initially offered me $9000.00 to settle, using "AutoSource" as their source to determine the cycle's valuation.  I provided the insurance company with a list of aftermarket parts totaling $8400.00+ that I had either had installed on the Wing, used in the course of its operation. They accepted receipt of the list but later ignored it, later offering $12,700.00. They claim their reason for not agreeing to have the cycle repaired is that regardless of the Honda mechanic's assessment, additional damage and expense "might" be noted.
How can I fight the insurance company and get compensatory damages from them?