Often the stator has failed and the regulator gets the blame. A stator is difficult to check completely as they sometimes have thermal breakdowns that only fail when hot. On Turbos, stators live in a VERY hot environment. So, the best practice is frequent oil changes and to replace the stator every 20K miles. Along with cam chain and tensioner/guide blades and water pump seal this becomes the infamous “triple by-pass” on CX500s. The CX650s are harder on the starter drive parts, so those are also replaced at 20K as preventative maintenance …hence the “quadruple by-pass."
These simple checks will find some bad stators, but a stator that passes these checks may still be defective under load and heat.
1. Honda Turbos have a 3-phase stator. These are the 3 yellow wires that connect from the stator to the rectifier / regulator. Check the resistance between the phases. This should be a very low value …under 1 or 2 ohms. Practically speaking, this is no resistance. The resistance between each of the 3 lead combinations (AB, AC, BC) should be equal. If you see higher resistance, or unequal resistances, the stator is bad.
2. Check the resistance of each yellow wire (phase) to ground, it should be well over 10 Meg ohms. Practically speaking, this is infinite resistance.
3. Battery condition is important. No regulator can make up for a bad or weak battery. Have it load tested, or simply replace it if there is any doubt. Always start with a fully charged battery!
4. All connections in a motorcycle’s charging system should be properly crimped. Crimping was invented by AMP Incorporated in 1941 as a “solderless” method for terminating wires and connectors in military applications. When done right, a crimped connection can be much stronger and longer lasting than a soldered connection. It should have equal electrical resistance to the equivalent length of wire alone!
5. Crimped connections are less susceptible to failure from vibration or fatigue. A properly done crimp is also gas-tight as well, not allowing oxidation to degrade it over time. Practically speaking, all Honda factory connections are crimped.
6. Use the right crimping tool and practice on scraps of wire to develop “feel” for the proper crimping technique.