Hi all, bit of a niggle has arisen with my 93 Superfour, wondered if anyone could help.

Last week, upon returning home from work, the bike died when finally reaching home. Wasn't a stutter or a stall, just ground to a halt. The next morning, the bike wouldn't start on the starter button - could barely turn the starter motor over and would only fire for a couple of seconds when bumping before dying again.

Checked the battery - it was showing about 11 volts with the engine not running. Charged it up for a few hours and tried again. Still no joy so I thought the battery was dead (was an unknown age after all). Bought a new Yuasa and the bike fired up normally and has been alright this passed week. Whilst doing so I checked the terminals again - 12.6 volts from new, but with the engine running (and revved to 5k to check the rectifier), it seemed to only run up to 13 volts or so (my other 400s seem to run up to and stop at 14 volts).

This passed week the bike's been okay, but wouldn't start again yesterday - ended up having to bump the bike after removing the fuse to the headlight (to give the electrics a little more power). Ran fine on the way home, albeit with no headlight.

What could be causing this? Overreactive rectifier not letting enough charge into the battery? (Haven't known of that before).

Here's what Honda manual says:-
6. Regulator/Rectifier System Inspection
Check the voltage and resistance at the regulator/rectifier connector (yellow & yellow) 0.1 to 0.5 ohms
Red & green battery voltage should register
Are the results of checked voltage and resistance correct?
YES – Replace regulator/rectifier (page 18-8).
NO – • Check for open circuit in the related wires.
• Check the related connectors for loose or poor contacts.
• Check for short circuit in the wire harness.

p.s. the rectifier/regulator is a known weak spot

Replace the reg rectifier

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I would check your alternator. Im not certain so recheck with a book or an eleccy friend but I think the yellow wires going upto the reg/rec should be around 50v ac at 5000rpm. But I agree the regulater is also a culprit, usually i found it would go over 15 volts at 3000rpm when it went duff, not stopping at 13v as yours appear.