Miss and carb tuning troubleshooting

compression test? leak down test? plug reading?
I like the spacer idea. I like the carb kit, because the needle and seat may be leaking, especially when hot. Immediately after hot shut down, look down the primaries. Do you see any wisps of smoke rising up, or a fog of vaporized fuel. That usually means worn needle and seat, and/or too high float level.