S/G questions?
 

Being new to Cubs, I have a couple questions on the S/G system, and how it works. I have a Cub Original, and a 100. I have rebuilt both S/G's, and the 100 has a new V/R. Both have new batteries. I may be going about it wrong, but to verify the system is charging, I use a voltmeter and ground it at the battery, and touch the BAT terminal on the S/G with the other lead. On the "O", I get a 9-10V reading, but on the 100 the V will range from 1 to around 14, and spikes back and forth. My questions are: Is this normal? Is the S/G supposed to charge the batt, or just generate enough voltage to keep the engine firing? Thanks for help in advance!

The S/G serves two purposes. (A) Starts the engine, and (B) Charges the battery, hence the name Starter/Generator or S/G.

The indications you should see is with the engine at full throttle at the battery would around ~14.0 VDC.

This is in consideration, that all is performing as it should.

If you see lower than 14.0 VDC, then it will mostly likely be a bad (or incorrect) V/R and/or bad wire connections in the "charging circuit" to include grounding.

Just hook up the test leads to the battery. + to + -to- .You should get around 13-14 volts when running.