yeah, the 'power pack' should be a magneto replacement.

what do i know though, i'm getting all this from remembering how to repair my line trimmers. the magnetos tended to crap out on the ones we used in the rain. the guy in the saw shop said their chainsaws do the same thing when left exposed to the elements for extended periods of time.

it could be the kill switch but you could rule that in or out by testing it with a voltmeter or even a check light.

i'm banking on my original diagnosis. I'm not a small engine mechanic, i just play one on the internet.

good luck