Voltage regulators Suzuki A50P

[Gixxer18]

Evening Gents, I've bought a Suzuki A50P moped, it's a 1974 MY but an E4 French spec bike, which differs from the UK version in a few ways, firstly the Air filter is a cylinder, rather than the oval UK shape, not a problem, I've managed to find a replacement filter.
There is no front brake light switch, but the wiring is there in the Loom.
The pedals mechanism works, but the chain is missing.
It has a reed valve instead of the rotary disc induction system, and the engine runs for a few seconds before dying, the tank is rusty inside, and I have removed the carb for ultrasound cleaning, just waiting on a carb gasket kit. There was a lot of crud in the carb bowl, the drain plug was blocked.
I've ordered new tyres, but they won't be here before 1st week of March.
The headlight is wierd. It's got a 6V, 6W "City Light" with no Hi or Lo beam ( the Left handlebar switch is blanked with a plastic clip where the dip switch should be.) which is not much use for lighting your way, and I want to replace it with an LED Headlight, H4 bulb, in a new glass unit, which I've sourced, and will fit in the bucket.
The ignition is powered by the flywheel magneto,so is independent from the battery, which I have replaced with motobatt MBT6N4 same as fitted to my A100.
Which leaves the AC generator. the manual states it gives out about 21W, and the fuse is rated at 15A which seems a bit high? 5A would probably suffice. There is a 1/2 wave rectifier,
To produce the DC thats probably Ok for incandescent bulbs, but might fry the LED Bulbs if the Voltage gives much over 7 to 9V since there is no regulator, the circuit uses the battery for that, which again is probably OK at night, and because during the daytime, there is a 6 Ohm resistor switched in.
So the bike has indicators, 8W each (x2) plus a speedo blinker idiot light 1.7W, a 21/5W Stop and Tail, 3W speedo illumination, and 1.7W neutral light.
With the battery fully charged, there is just enough wattage available at night to have a 15 W headlight and the tail light on with the engine running at about 5000 RPM. Hence the reason I want to fit an LED headlight, or not go out at night!
I have got new handlebar switches off an online store, which have Hi/Lo and front brake switch fitted, and I've replaced the Loom with new wire and shiny bullet connectors, and I've added an extra ground wire from the headlight to the tail, and a jumper up to the handlebars for the horn ground.
So to use LED's safely, I need a stable DC voltage supply, and the bike hasn't got a regulator/rectifier fitted.
I can make a full wave bridge rectifier out of four 1N4007 diodes, which takes care of the Ac to Dc, but has any one got any suggestions or ideas for a 6V regulator design good for about 3.5 to 5A?
Thanks for reading this far!

[Alan H]

The battery 'should' be ok as a regulator, but the 5a fuse won't be big enough. With everything on you've the thick end of 50 watts there, so at 6v (actually about 7.5v when running fast, you'll be pulling 7 amps. You'd have been better sticking to a lead acid battery (more likely to keep going with such a charging system as agp batteries don't like abuse!)
Good idea with the dipswitch & led headlamp, but even with a full wave rectifier you'll not gain a deal of charge due to the tiny alternator, but if you really want to go full wave, try one of this type of rectifier(ebay 193486765128) - way overspec, but that's better than not enough. I put one on the T200 and it was fine though, but that has a 6 coil alternator and uses the light switch as a regulator.
Just a thought, if the alternator is earthed, you're stuck with half wave charging - I haven't a wiring diagram, so can't check that.