SF1 Fuses
- Thread starter RJS
- Start date
Rob
Hero member
- Location
- Midlands, UK
I think you're correct with 3x8A fuses. 40 is overkill for the main supply to the ignition switch - I'd suggest 16A which I think is what the factory specified. If you squint at the owners handbook wiring diagram you can just about make the number out!
piranha-bro2
Hero member
- Location
- Melbourne
That sounds right Rob. 3 x 8A and 1 x 16A.
Dellortoman
Hero member
- Location
- Tasmania, Australia
It seems your bike is a bit of a mystery if it has 4 fuses.
Wiring diagram for SF models shows only two fuses. One for the stop lamp bulb only (weird, the triples did that too) and one for the feed to the main ignition switch that serves everything else on the bike. There's no fuse in the charging circuit between the generator and the battery.
If only 2 of the fuse positions are connected, then you can probably assume your wiring is basically original, and the 4-fuse box is simply a replacement for the original 2-fuse job. Fuse boxes for 4 blade type fuses are common and cheap. 2-fuse boxes are a rarity. Lucas does a couple of old black plastic ones for glass or ceramic fuses (used in old pommy cars). Anyway, proceed as others have suggested above. 16A for the main switch and 8A for the stop lamp.
If all 4 fuse positions are active (have wires connected to them), then it's a fair indication that the bike may have been re-wired. In that case your first job is to work out what each fuse does. Perhaps whoever did the wiring job put a fuse in the charging circuit, between voltage regulator and battery (or between VR and starter motor cable). If so, that'll have the thickest wires connected to it and might need a fuse of about 25A or 30A. 16A sounds about right for the ignition switch fuse, and the others sized according to the smallest wire size in the circuit that each fuse serves (the fuses are there to protect the wiring from melting if short-circuited). If the wires look a bit puny, try 8A, if they regularly blow under normal use (no faults in the wiring), go up to 10A fuses.
If your bike has electrical accessories like fog lights, heated grips, a 12V outlet for heated underpants or phone charging, or anything else, that could explain the additional fuses. The best advice I can offer is to get to know your electrical system.
Wiring diagram for SF models shows only two fuses. One for the stop lamp bulb only (weird, the triples did that too) and one for the feed to the main ignition switch that serves everything else on the bike. There's no fuse in the charging circuit between the generator and the battery.
If only 2 of the fuse positions are connected, then you can probably assume your wiring is basically original, and the 4-fuse box is simply a replacement for the original 2-fuse job. Fuse boxes for 4 blade type fuses are common and cheap. 2-fuse boxes are a rarity. Lucas does a couple of old black plastic ones for glass or ceramic fuses (used in old pommy cars). Anyway, proceed as others have suggested above. 16A for the main switch and 8A for the stop lamp.
If all 4 fuse positions are active (have wires connected to them), then it's a fair indication that the bike may have been re-wired. In that case your first job is to work out what each fuse does. Perhaps whoever did the wiring job put a fuse in the charging circuit, between voltage regulator and battery (or between VR and starter motor cable). If so, that'll have the thickest wires connected to it and might need a fuse of about 25A or 30A. 16A sounds about right for the ignition switch fuse, and the others sized according to the smallest wire size in the circuit that each fuse serves (the fuses are there to protect the wiring from melting if short-circuited). If the wires look a bit puny, try 8A, if they regularly blow under normal use (no faults in the wiring), go up to 10A fuses.
If your bike has electrical accessories like fog lights, heated grips, a 12V outlet for heated underpants or phone charging, or anything else, that could explain the additional fuses. The best advice I can offer is to get to know your electrical system.
motoddrob
Hero member
- Location
- S/W Australia
Maybe your looking at the earlier models diagram but Sf1 onwards had 4 fuses
Dellortoman
Hero member
- Location
- Tasmania, Australia
OK. Thanks. The only wiring diagram I could find for the 750s was the twin fuse version.