Hi Andy,

I had a hard time trying to describe the "undercut" and your "hollowed around" is a probably better description. The holes are opposite each other. I'll put a picture at the end of this post, hopefully it will help. Again, this was a rear needle valve engine. My drawings are not the best, but I hope it helps. If you want to check, the brass insert is removed by:
1. Remove carb from engine
2. Remove carb barrel
3. Remove fuel nipple and needle valve or nut - what ever applies to your carb.
4. Put carb on a piece of hard wood, then place a piece of hardwood on threaded end of brass insert and GENTLY tap it out.
5. To replace brass insert. Line up the fuel intake hole and start the insertion of the brass insert into its seat with finger pressure. Take a dowel with a drilled out center (or a hollow brass punch) and GENTLY tap the insert back into place.

I never did swap carbs on my engines, but both engines are working well now, so it wouldn't be much help. I did three things at once when I fixed the problem, that is, I drilled the intake nipple, drilled the exhaust nipple and drilled the brass insert - I wish I had done one at a time to isolate the problem.

I'll take a look at the mecoa site, thanks for pointing this out to me.

Thanks for keeping us up to date.

Fly4Fun,

Wayne