Yeah mate, that's it, it's called a "solonoid" though, which is "old time speak" for starter relay, ha ha!
Trace the wiring from your right switch block into your headlight, from memory you need to look for a black and white wire, and a black wire to make that starter button work, but while you're there, check 'em all.
I'm crap at electrics, so I don't use a multi meter much, just a little test light, and that's gotten me by for the last 38 years of playing with old bikes, ha ha! Cheers, Terry.