I’m in the process of converting my 1964 Venom to 12V. I read Stuart Francis’ electrical article in RC186 which was a great help. I have fitted an alternator and electronic ignition. Is it safe to fit a standard 30 amp fuse, or should I fit a fusebox? How many connections and to what wiring? Ron Savage
Most simple motorcycles cope very well with just a single fuse in the battery lead. The main hazard is from the battery and the possibility of fire from damaged wiring. Once the battery is isolated, any short on the wiring will soon kill the ignition and the engine will stop. As for fuse rating, 30A will allow a considerable fault current. The actual load in normal use is unlikely to reach even 10A (120watts). A 20A fuse is more than enough. Dee Jackson
Fit a multi-fuse box. Available from Vehicle Wiring Supplies for peanuts and makes faultfinding a doddle. I also still fit a main fuse on the non-earth side of the battery and agree with Dee, 20 amps is more than sufficient. Lawrence Howes
The primary purpose of the fuse is protect the battery from an overload /short circuit in the wiring or electrical loads. 30 amps is way too much; you could easily melt the wiring with that current as you would be dissipating 420W – 30 amps x 14V of a fully charged battery. A 10 amp fuse should be more than enough. I would keep it simple with a single inline blade fuse from the battery on the supply side. I would only add additional fuses if you were connecting modern high current accessories like heated grips. Stuart Francis
My 1960 big head Bullet came with a Boyer ignition and an alternator. I added a six-fuse spade fusebox from eBay, with separate fuses for main feed to the ammeter, ignition, indicators, lights and brake light. I also fitted heated grips as I’m a wus, and I fitted indicators as I don’t trust car drivers to understand hand signals.
All wires, connectors and indicators came from Vehicle Wiring Products, with rubber stemmed indicators at £12 per pair.