Battery fully charged but only getting a clicking from the starter relay

Hi there,
we have the same beautiful machine (stelvio 08) and the same problem. Sometimes start from the button - starter and other times not! The problem is that the commander read 12.6 V or little low. The commander must read 12.7 and over to give the ok and start the machine. I think we have somewhere a very week cable (or hot)! I made a temporarily solution that works perfect. I put a new cable from engine starter to my battery with a new start button. I make a bypass until i find the right solution.

If the battery is fully charged (test it with a good volt meter), and the solenoid is good (prove this by measuring the volts on the battery side of the solenoid when pressing the start button) and it still will not start, suspect the starter or the wire from the soleniod to the starter.

Your battery can read proper voltage and still be bad. It probably fails under load. If your alternator is putting out charging voltage and your batteries are going bad it is usually because of corrosion in the wiring connections. Start at the black ground wire attached to the engine block. Remove the wire use a wire brush or light sandpaper and clean the terminals and the area where the connector touches the block. Apply a light coat of spark plug grease on the connection after reinstalling. Check the wire terminal for corrosion in the wire also. Follow that wire back to the next connection and do the same. Do this until you have cleaned all the terminal connections. Then do the same with the red positive wire starting at the starter and alternator. When that is complete check your battery voltage it should be 12.5 to 13 with the engine off. depending on its state of charge. Start the engine and read the battery voltage at the battery again. It should read between 13.5 to 14.3 VDC
If it does not read at least 1 to 1.5 volts higher with the engine at 2-3000 RPM you have a bad alternator or regular. If it reads too high your regular needs replacement. Cleaning the wire and wire terminal connection solves most electrical problem on motorcycles. Cost nothing to do but take a little time. For the plug type connectors get some contact cleaner, spray both male and female allow to dry and plug back together. Good Luck