Engine electrics; 1984 ATC200 Big Red

[Jon]

Need some electrical help over here in the UK please...
Just riding along, (machine running fine) when the engine stopped - just like the key had been switched off. No splutter or mis-fire, just stopped.
Towed it home, checked for spark - no spark at all.
Checked wiring - all fine.
Tried another spark plug - still no spark.
Checked for output from pickup on camshaft - get a tiny pulse when cranking (digital multimeter's not too good at seeing a quick pulse, but it showed 0.1v briefly).
Tried the coil - just dabbing LT wire straight onto battery - get a spark at the spark plug OK then.
The battery's good, the starter works fine.
Think it's probably either the alternator or the CDI unit. (CDI unit has the round connector with 6 pins).
Can anyone please advise how to test the CDI box, and the alternator output to the CDI box? I need to try and diagnose which (if either) is faulty.

Any other suggestions? Thank you!

[Howdy]

Check the stator ( altenator ) first. Unplug the black with red striped wire coming from the stator. Get a ohm reading on it. Take one lead to the terminal and the other to lead to the bare metal on the motor. You should have 215-240 ohms. Once you eliminated the stator then move to the next item ( CDI, Kill switch, wiring harness, ect ).
Howdy

Howdy

[Jon]

Thanks Howdy - unplugged the black & red wire to the CDI, and checked for resistance between the casing and the wire into alternator. It's an open circuit!
Will open up the alternator case tonight for a look.