My 1980 GL1100 now after many electrical repairs idles at up to 14.7-14.9 VDC. It will max out at 15.02 VDC. Problems resolved to get that voltage included: Low battery juice, greased up connections, crud on all electrical connectors, mis-wired wires, wires taped with Chinese tar paper, real cheap electrical tape, routing of wires into sharp turns, sharp edges, loose connections, dirty fuses, dirty fuse holders, dirty starter connections, greased up starter relay, fouled light sockets.
The alternator output was at 50+ ACV but the system never saw it since the connector was filthy. I left the connector in circuit since it was still pliable and not burnt and now spotless. You can use heat shrink tubes after soldering connections, but put them on before soldering with resin core and as an adder use room temperature vulcanizing (RTV) caulk on the joint and then heat the heat shrink. You can buy heat shrink tubing with RTV inside, but expensive.
All grounding terminations on an older bike need to be opened, cleaned so all metals are bright and then re-assembled. Verify with an X1 Ohm meter that resistance is as close to zero as possible. Again no grease.
On the battery side of things be sure to clean all, let me repeat, all connections. The copper needs to shine, the lead needs to be bright grey, then join the wire to the terminals. Do not apply grease, no dielectric grease. If you cannot maintain clean contacts go to your local electrical supply house and buy a pound of Duxseal by GE. This stuff is wrapped in cellophane, feels like play dough, will never harden, will never deteriorate and seals water like a duck's a**. It forms to any shape and can be placed on the + teriminal and allows a jumper cable to be installed through it, can be peeled off, it does not melt or leak and run like grease and will never get between the joints of an electrical connection. It beats the hell out of dielectric grease and by the way almost all grease is dielecectic at 12 VDC. The problem with grease is at high temps it runs and gets into everything and then with a thin film bewteen joints resistance increases and the next thing you know you have electrical problems. To keep moisture out use duxseal
Duxseal is great for vacuum leaks, simply press it where you think the leak is and voila no leak. This grey soft pliable material should be carried with you as an emergency repair kit for leaks. If you know an electrician ask him for some.