If it gets too hot and un-solders the wire, try silver solder, or any Rohs-compliant solder for printed circuit boards, they also have higher melting temperature than the “traditional” lead-tin solders.

It seems that the lead on the ground brush of the Leopard starter is prone to breaking.  Mine recently broke and the box of parts I got with the used kart had several ground brushes with broken leads as well as a starter with a broken lead on the ground brush.  It appears that the previous owner had repaired some and had applied silicone (RTV) to all the brush leads.  He may have believed that vibration was causing fatigue failure.  But the silicone didn’t seem to end the problems.  Are there any other theories (or even facts) about the cause of failures?  One possibility might be that inadvertently hitting the green “start” button while the engine is running could cause the Bendix to engage and spin up the starter to a point where the brush is damaged.  I know that there’s a similar issue in motorcycle-engined racecars (I have one).  If  the car spins and travels backwards for any distance before the clutch is depressed, it kills the starter (which has a one-way sprag clutch rather than a Bendix).  The starter failure there often involves killing the brush assembly (ask me how I know).  I’m considering putting a flip-up cover over the Leopard’s “start” button to prevent accidental engagement.  Any suggestions?  Thoughts?