BATTERY DRAIN
Ben Jackson’s new to the world of classic bikes and describes himself as clueless with electrics. The battery on Ben’s CD175 discharges within a few days if left. He adds: “Manuals seem to speak a language I don’t understand”. Well, you’re not alone there, Ben!
A wire harness can be intimidating, so it’s important to work out the most likely problem areas and focus on them, one at a time – and don’t overlook the obvious. For example, the first step here is to make sure it’s not just a tired battery by disconnecting it and seeing if it still drains. If not, there must be a leak in the system.
It’s unlikely to be a ‘short’, like a pinched wire, as this would get hot or blow a fuse and since it’s happening with the ignition off (assuming the ignition is switching off) then it’s likely to be in the charging circuit – generator to battery. My guess is the regulator/ rectifier, although I think they’re separate on a CD175.
The rectifier contains diodes – one-way electricity valves. If these fail and open both ways, battery current can leak back through. It’s easy to check; try disconnecting each component – rectifier, regulator and generator – one at a time (carefully noting the wire connections) and if the battery stops discharging, you’ve found the offender. It’ll take longer than using a meter, but might be the difference between having a go yourself and paying somebody else. It’s not just the money, DIY is very satisfying when it works and adds confidence to try another challenge – and with old bikes there are usually plenty!