Was trying out a new tacho tonight, and when nothing happened I thought "put the old one back in & check it still works". It didn't.
So, I poked about with the multimeter. Everything off (main switch)- battery voltage 12.3V. Engine at idle, 12.3V Revved to a guestimated 2K, still 12.3V. Most I got out the tacho signal wire with the meter set to AC was 1.3-ish variable. Got the same 12.3 out the switched +ve, which on this engine hangs off the rectifier out via a fuse that I proved OK.
Now, I am aware that the tacho signal at idle on a 6 pole alternator is in the region of 180 Hz, so the reading on the meter is nothing like accurate, but my memory of doing a similar test on my Yam 55 it showed something in the region of 5V.
1) based on that, thoughts? (I have a theory, but not going to bias your opinions with it yet, other than to say "pass me the flywheel puller"
2) could anyone else with a Clamshell 3 cyl 50 or 60 measure the batt voltage with the engine both idling and at 2K rpm. An AC volts reading on the tacho signal wire would also be much appreciated.
In summary I don't have a good feeling about this......