I disagree quinten, a decent alternator has the ability to put out more than enough juice to power ignition and lighting at tick over with a cap of some form fitted. If I’m running the bike and a fault occurs in the wiring and happens to blow the battery fuse, normally the bike would die and you’d trouble shoot the issue, if there’s a cap fitted then it would run off the cap, until a) the fuse on the cap fails for the same reason, b) the fault then causes causes the cap to leak and fail.

You could put a single fuse between your grounding point or your live feed and then have the cap connected directly to the battery... this would work. But it also removes the advantage of having the cap (or a regulator rectifier unit with capacitance built in, the Boyer I mentioned was the Boyer power box, not the Boyer electronic ignition) so by the cap abs the battery having separate fuses, should you have an issue with the battery or lend your battery to a mate so he can continue his ride wink then you’d just disconnect the battery fuse (insulate the live lead if this isn’t the fused end and you’ve taken the battery off) and run the bike as normal.

The cap is like having a second battery, like the battery it will give a steady flow of DC power through the loom, and will remove all the peaks and troughs of voltage from the reg/rec which is ultimately what the battery is doing once it’s reached full charge. However unlike the battery, if you stopped the engine you’d be lucky if you got a toot from the horn. Any stored charge is lost very quickly once a circuit has been made.

But I’m no expert, I’d be interested to hear Stuart or NickL’s opinion to that?

Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (now rebuilt)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)