I know very little about carburetted engines, but most carburettors run several different fuel jets. Each is involved is a specific phase of engine warm-up (fast idle, idle, etc.). If you haven't, I would check to make sure the jets aren't clogged.
Hopefully someone else will be more helpful. BTW, I'd try
www.crxcommunity.com. They mostly deal with 2nd gen. stuff, but many are knowledgeable and I've seen a few 1st gen. owners do rebuilds/etc.