Electrical questions

[Hoopy]

My 1950 cub of 20 years came to me without a generator. I decided to rectify that this past month. I purchased a used generator with cut-out and a new Brillmam wiring harness appropriate for the serial number.
I attached the Generator and tested its functionality. I then installed the new harness.
I re-assembled the hood and connected the headlights.
WIthout repolarizing the generator, I tried to start the engine.
It cranked twice, then nothing. The starter doesn't crank.
I thought it might be the fuse ( I didn't turn on the lights) but the fuse is fine.
So, what happened?
I assume it is the starter. Could it have failed at random, or could I have damaged it?
Another thought I have. When I bought the tractor, it had no generator. Presumably, the prior owner also had generator issues and removed it. Could it be that the 4 position switch is bad, causing a short of some sort.
Your thoughts are appreciated.

One other questions regarding the cubs positive ground system, which I do not comprehend. Anyway, if I want to test a component( say lights or generator) with the battery cables are properly connected, could I run a jumper from the negative (power ) terminal to the item? If the battery was disconnected, would I run the jumper the same way or from the positive terminal. See, I really don't get it.

Thanks,

John

PS the wiring diagrams from this sight have been helpful

[Bill V in Md]

Regarding the cranking problem, my guess is that you have a ground connection that is not making good contact. I have had the same problem where one minute it is cranking and the next minute there is nothing (no sound). If this is the case, corrosion is likely the culprit. Make sure the connection of the battery positive to ground is clean (no paint/no rust) and tight. The bolted connection of the starter to the tractor frame must also be clean (metal to metal). The poor connections are not limited to the grounds, and could be on the power/negative side. In this case the problem could be the starter switch is not making good contact when you pull the the starter rod. These switches can get dirty or wear out and may need cleaning up or replacing.
Regarding the lights, yes you can run a jumper from the battery negative to the light terminal. Remember the lights use their metal housing to make a ground connection to complete the circuit. So any corrosion on the bolted connection of the light housing to the bracket/tractor frame must also be clean. If the battery is disconnected, you still run the jumper the same way.

[tst]

good grounds and connections, starter switch contact check where it meets the starter also,

[Hoopy]

Thanks, gents.

[Eugene]

I tried to start the engine. It cranked twice, then nothing. The starter doesn't crank.

Battery condition and I don't mean new? Conduct voltage drop tests.

Edit. Why didn't you install a single wire 12 volt alternator?

[Hoopy]

I wanted to stick to the original configuration.

[Eugene]

Curiosity. Web search for 12 volt single wire alternators that look like a Delco generator. Several listed. My opinion, high priced.

One example, Powermaster PowerGEN 1955-64 GM 1-Wire Alternators, 12-Volt