It can also be useful to place the recommended tire pressure label on the tire next to the valve stem. Install one bead on the rim. Install the second bead beginning at the valve.
First, if a tire requires a replacement valve-stem core, choose a stainless steel core. The brass cores corrode. The stainless steel core costs about $2. A corrosion damaged sensor costs about $100. It's worth investing in the stainless core.
Many motorcycles use fairly wide, low profile tires, and obtaining a good bead seal can be difficult. If your air pressure and CFM is high enough, sometimes the bead will seal by moving the tire around on the rim. Probably a trip to a motorcycle repair shop would solve the problem.