The Trouble With Batteries....
Author: Tri-Spark Date Posted:23 November 2022
Your electronic Ignition relies on power from the battery for its operation so it only makes sense to look at the battery when trouble arises with engine performance.
If batteries just lost a bit of capacity as they aged we would notice this and plan to get a new one in due course. Unfortunately they die in strange ways and sometimes suddenly, resulting in some of the most common troubles with our old bikes.
Here's what can happen. A battery with no load on it (everything turned off) may check out OK close to the nominal 12 volts but once the lights are switched on it may suddenly drop below 10 or even lower down to 8 or 5 volts. This is typical of an aged battery that's heavily sulphated but we can check for this by load testing the battery.
A bike shop can load test your battery or you can simply monitor the voltage with a meter for a few minutes with the headlight on (motor off). A good battery will power the lights for several minutes while maintaining above 12 volts.
Sometimes a battery can have one cell that dies resulting in really strange things happening. The lights and horn may still work OK giving the impression that the battery is good when in fact it's struggling to function. The damaged battery can cause the ignition to misfire as the voltage fluctuates wildly under charge from the alternator.
In some cases we've even seen batteries that have short circuited to the frame or seat, burning out the wiring harness as a result. This can happen on some triumph twins if the battery posts are facing forward toward the fuel tank. Take care when buying a replacement battery that the terminals (positive and negative) are the same way around as the original.
If your battery fails to maintain its charge it should be replaced without delay to avoid future headaches.
Wiring harness - burnoutBy: J. Phinizy on 24 November 2022Your observation about a burned out harness is spot on! It happened years ago on my T140. What a pain. Not only do I use a cut piece of inner-tube as a "cover" or mat to shield the terminals but also improved the ground as the factory harness used a too light gauge ground wire. - Jay