I purchased a brand new 2014 bike and bought a lot of reputable brand names after market parts that are equivalent to OEM if not better. They were installed by the same dealer I purchased the bike from, the throttle got stuck which lead me to loose control and crash causing me severe injury. I also took the bike there regularly for maintenance, so I don’t know how they never notice such a problem. I have liability insurance only, I wasn’t under the influence when i crashed either. They had a brake pad holding pin off one of my motorcycles before in the past and I never took action except for there apologies. The Bike has a recall on it but it was not related to the throttle but they never performed the fix even though it was refundable by the manufacture.
In order to prove that the dealer improperly installed the throttle grips, the motorcycle would need to be inspected (in its condition after the crash, and before making any changes to the throttle grips in question) to determine the validity of the allegation that they were improperly installed. This would need to be determined by an independent, qualified and experienced motorcycle mechanic (an expert witness), which usually costs significant dollars. There would also be a question about the need to install non-OEM throttle grips on a relatively new 2014 motorcycle, as well as the manner in which the motorcycle was being operated at the time of the crash and the experience of the driver. Also, documents from the dealer regarding the installation of these throttle grips would need to be reviewed to see what the dealer indicates about the work they performed, etc.