nsrmonkey wrote:I may be wrong bit I think the issue with the 400s is with it burning the switch out as well as the reg rect.

Oh no mate, you're 100% spot on. The stock setup cannot handle UK spec 55/60w H4 bulbs. Jap bulbs are 35w on the headlight.
Uk spec VFR400's had a relay, RVF400's and Jap VFR400's run the headlights (35w) straight through the switch and the main beam (60w) through a relay.
That switch (the push button on the l/h switch gear) is what burns out and when it does so your headlights go out!

There was once a how to wire the headlights via a relay thing on 400greybike, possibly written by LP.............

Not sure about the '18 and '21 but the '28 does run the headlight through a relay so it shouldn't matter.
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