Testing Alternator etc

[SteveD CB500K0]

I’ve got one of them Al

The AVO - not the modern digi-thing.


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[Bryanj]

Very true Al but Megger was the name on the one i had, but then 17th edition outlawed mine as it used a fraction less of a milliamp to test than was writted down!

[BigAl (Alan)]

They are a nice bit of kit...much better than the old wind-up 'Megger' - insulation tester as image...no batteries required!

[Sesman]

Megga….Excellent tool for measuring the insulation resistance of apprentices.

[ST1100]

They are a nice bit of kit...much better than the old wind-up 'Megger' - insulation tester as image...no batteries required!

The first HIOKI we had ran on a 9V block battery... loved that analogue thing, so easy to read...
Those digital displays (SODIAL VC60B+) always take a moment to decipher...

[Mike_Berkshire]

First check that the field coil is getting energized with the key on engine off. Take the left honda nameplate off.
With the key on the three screws should become magnetic. Check with any steel object. The fiels coil is fed by 3 yellow wires #6  in diagram.

I had a spare 5 mins last night so nipped into the shed test if the screws were magnetised when ignition on; they were not. I am assuming it is the three inner screws you mean; the ones that sit in the counterbored holes?

[Bryanj]

Try putting a jumper wire from battery positive to the white regulator wire and see if they magnetize then, if yes reg or wiring  if not wiring or coil

[Mike_Berkshire]

Cheers Bryan. I’m capable of that and will try and find a few mins to do that tomorrow.

[Mike_Berkshire]

Rather than fit a jumper cable fro the battery I probed the white wire at the regulator. It was showing 12 volts but not magnetism at the alternator screws. I’m polishing the wheel hubs now to get ready for wheel rebuild so once that’s done I’ll get back on the alternator.

[Oddjob]

I’d check there is still 12v on the white cable where it joins the field coil. If there isn’t then there’s your problem. If there is then maybe the field coil has failed for some reason.

[BigAl (Alan)]

Just out of interest, what is the field coil resistance on a CB550?...I know the CB750 is around 7.5ohms (4.4ohms on the CB750A)

[Bryanj]

Cany remember off hand but download the proper manual from alladibs cave

[Mike_Berkshire]

I have tried to access the manual in Alladins cave but for some reason I can open it or download it; I will try again later as our internet connection is a bit flaky and it might just be a connectivity issue. In the meantime, although this is all a bit of a dark art to me, I have tested that the white wire terminal out of the regulator to the field coil is live; it is. The voltage at the earth connection of the field coil is 12 volts too. The resistance of the stator coil windings are between 0.6 Ohm and 0.8 Ohm so there is continuity there but differing resistance. Despite the fact the filed coil is being energised there is no magnetism in the three bolts that hold it to the alternator casing; could it be that stainless bolts have replaced the originals and would that matter? I cant think of what to try next without the manual so I will keep trying to access it or find it elsewhere.

Are the stator coil winding resistances OK?

[Mike_Berkshire]

Has anyone used one fo the replacement combined regulator rectifiers like DS sell in this charging circuit and if so what thoughts? An upgrade to a more modern integrated unit could be a good upgrade?

[Bryanj]

Disconnect the white wire at reg and check resistance to ground, with power off obviously. The white and green wires have connectors behind the sprocket cover that can fail