higher output alternator to get more power for a high wattage halogen headlight but this would rob some power from the engine and seems a less elegant solution.
I plan to use this regularly (alongside my Tiger 800 XRX) rather than let it be a garage queen
A single horsepower is 735 Watts. The most powerful alternator capable of being fitted to these bikes without major modification produces 240 Watts (if its maker is to be believed, no technical data has ever been made available).
Without an upgraded alternator, your prospective bike's standard one produces 120W at 5,000 rpm, 75% at 2,400 rpm.
I bought a brand new electric start Triumph made only two years after the Tiger, with the same alternator. It was inadequate then. During 1978, the original Lucas company began offering 3-phase alternators that fitted in place of the previous single-phase; when I upgraded my Triumph, I chose the higher output one (180 Watts at 5,000 rpm, 85% at 2,400 rpm), I still have the bike, I have never had reason to regret the inelegant solution.
As you want to use the 73 Tiger regularly in place of your modern Tiger, even with LED lighting, it must generate at least 60 Watts reliably any time it is running. Maybe look around and see which other modern bikes have a 120W alternator ...? Ime, LED lights are a useful modern development. But they are still not an alternative or substitute for adequate generated power.
The bike is currently sitting about 460 miles away from me so I am not sure what the existing headlight arrangement is. I want to change all the lights including tail and flashers and am not too bothered if this involves fitting a replacement 7" reflector unit to achieve a compatible bulb fitting.
Headlight in particular, little wisdom in the ambition without knowing what is fitted to the bike now.
Standard fitting on most 1973 British bikes was a bulb base and lens/reflector made by the original Lucas company (as opposed to the current Wassell "Lucas") known as British Pre Focus; the 120 mph Triumph I bought brand new was fitted with that headlight. In those days, in the UK, headlights were generally just used for lighting the road in front of the vehicle at night, the Lucas BPF combination was absolutely appalling, as much use as the proverbial chocolate teapot, even at only the 60 mph national speed limit.
The original Lucas BPF bulbs and lens/reflectors had two problems - the dismal light output for the power consumed, the poor lens/reflector design that did not focus the light that was produced. The original Lucas company produced BPF bulbs and lens/reflectors of at least two different designs, but any combination is just different degrees of abysmal.
The BPF LED does produce more light than any original Lucas or modern pattern incandescent BPF bulb, but it does not solve the poor lens/reflector design, neither of the originals nor of the current Wassell Lucas production.
That is why I asked:-
When you intend to use the bike - just in daylight or at night as well?
... just in daylight, BPF LED in matching lens/reflector appears to be 'good' for daylight riding, in that the poor-design lens/reflectors scatter the light over a wide arc; however, at night, you want the light focussed in front of the bike, which none of the BPF lens/reflectors can or could ever do.
The "H4" LED replacement shown on the CDRC webpage is the current automotive standard P43t bulb base ("H4" is just the three spade terminals electrical connection). However, £50, doubtless plus p&p and VAT, is a vast expense for fairly ordinary light output compared to the best quartz halogen bulbs, which cost a fraction of that, can be had post free from the likes of Amazon. If the bike does not have a P43t lens/reflector already, that is another expense.
Whether or not your intention is a P43t LED bulb and matching lens/reflector, be aware the better the lens/reflector is at focussing the bulb's light in front of the bike, the worse it will be for daylight riding, when you want other road users to see the bike before they are almost directly in front of it ... Also note that a well focussed dip beam is brilliant (pun not intended) at shining in car drivers' rear view mirrors, not only is a dazzled driver an annoyed driver, he or she cannot judge the bike's distance accurately.
Many British motorcycle riders now in their sixties and seventies will have been city dispatch riders in their teens, twenties and possibly thirties. Based on first hand experience, the previous two paragraphs and not just on my old Triumphs (I do not own any modern bike), I use quartz halogen headlamp bulbs just for nightime riding in the dark, quartz halogen or 15W Eagle Eye LED pilot bulbs for nighttime riding under streetlights, daytime visibility to other road users. Powerful pilot bulb spreads light in a wide arc in front of the bike, good visibility to other road users without dazzling them, uses very little power, useful if low rpm (low alternator output) riding is required for any length of time.
The bike is currently sitting about 460 miles away
I want to change all the lights including tail and flashers
Afaik, CDRC does not sell a specific tail/brake LED replacement bulb that will work in the standard Lucas 73 onwards rear lamp. When you actually have the bike and can remove the rear lens, you will see the primary problem is the bulb holder holds the bulb vertically, not a problem with an incandescent but, because LED replacements are a mixture of red and white LED and individual LED are directional, one of Pete's LED replacements will emit fairly feeble light rearwards (because the white LED are intended to light the numberplate) while the numberplate will be lit brightly ... in red ...
LED replacement bulb that will work correctly in your bike's rear light.
If the bike is to be ridden lights on in daylight irrespective of ambient light, the primary purpose of replacing the rear incandescent with LED should be greater contrast between tail (always on) and brake, to reduce the chances of being rear ended, especially in bright sunlight - a CRDC "light board" that replaces bulb holder and reflector might be better than just a bulb replacement?
Similarly, replacing incandescent speedo and tacho bulbs with LED should be to improve the visibility of the faces at night (you will not know their standard lighting is poor). However, due to the design of the speedo and tacho, white might end up dazzling you by the time the single LED lights each face well, consider red LED which will less affect your ability to see in the dark.
Ime, converting indicators to LED is more trouble than it is worth. The visibility is not improved, the power saving is negligible, the cost is ridiculous, especially as a new relay is also required, the warning bulb in the headlamp shell must be rewired.
