Thanks for your info. I drilled out a stock AP carb. to 11/64" and used three Norvel glow gaskets with my Nelson adapter, it sounds like it has more RPM, this is with a stock cyl. I'm using these engines on a 1/16 scale toy tractor in a hobby called Micro-mini tractor pulling. Check out the web site at, www.nmmtpapullers.tripod.com. I have lots of Norvel engines rat holed away, but need to figure out the AP for when I use all of the Norvels.