It only takes one of the following questions to be overlooked. #1 battery connections, clean and tight, no corrosion at terminals where they make connection to the copper wire. At the battery, solenoid, and starter. This is where I suspect the problem lies because your volt meter leads may be touching the post and the cable lug to make a better connection, and that's why it starts when you test at the battery. The clicking noise is usually low voltage to the trigger on the solenoid. #2 Do your grounds connect to the engine BLOCK, not some piece of sheet metal that bolts to the block, both from the battery and the solenoid, preferably to the same lug on the engine block. If your battery has a short wire that grounds to the chassis, run a #6 ground wire from the battery directly to the block. #3 What are your voltages at the trigger and both sides of the solenoid, they should be 12.6v in your case. With the starter not turning, but in the start position (key) do you have 12.6 to the positive BOLT on the starter. testing the bolt, not the cable lug will eliminate another path of resistance. If 12.6 here bad ground where starter bolts to block, or an intermittent open in your new starter. Lets not go there yet. If the trigger is less than 12v I'd suspect a bad safety interlock switch/connection causing high resistance/low voltage. After you have checked ALL of these things, I would bypass the entire OPC (operator presence control) or safety switch circuit. Set the brake, make sure blades are disengaged, and the transmission is in neutral. Use a start switch, 2 wires hooked to a push button switch with alligator clips on the ends (best), or a screwdriver to make a circuit between the trigger and the battery side of the start solenoid. Enough for now, let us know the outcome, and we'll go from there. I assume this is a lawn tractor/mower with the Briggs V twin OHV, but if not all still applies. I don't know electrical, I have spent most of my life learning it! As "Astro" the dog on the Jetrsons cartoon used to say, Rots of ruck! 445A
