[Wisakedjack]

I am very happy to report that my carburetor issues have been resolved. While cleaning my carburetor this week I've discovered the following issues:

1. I think the main issue was that the idle screw was not seated completely when I was doing its adjusting. I got the new longer one from MM earlier this season and the fit was pretty tight, so I assumed it was screwed in all the way, when the conical tip was merely showing in the passage opening. In retrospect I should have realized the the spring should be fully compressed when the idle screw is all in. Having done this properly I did 3/4 turn out since I have PCV valve as an initial setting and it pretty much worked well.

2. I carefully cleaned the idle jet with small wire. I was not able to take it off since the screw driver slot is half gone. So, I had to do it in place. By the feel it was not completely clogged, but may have had some residue there.

3. I discovered that choke plate was put incorrectly. As a result the poppet valve was opening to the outside instead of inside. I think that explains why I always needed to open the choke right after the engine was started.

4. Finally, I replaced the throttle plate. The old one was somewhat bent and did not fully obscure the lower of the two idle holes. Whether that had any significant effect on how my carburetor worked I don't know.

After putting carburetor in the engine and minor adjusting I no longer have any issues with engine shutting off when I throttle down. In addition the engine idles nicely at 800 RPM. I don't think it ever sounded this good.

I would like to thank everyone here for advise and helpful suggestions. It was extremely valuable to learn few other possible causes (like PCV valve failure or cracking exhaust flange) even though they were not in play at this time. Thank you guys!