Astute observers of the national weather scene may have noted that we here in central Ohio are currently enjoying some of the first favorable flying conditions of the new year. Surely, those folks are wondering to themselves, "I wonder if Papa Golf will be flying this weekend?"
Well, no. Co-pilot Rick had graciously offered to stop by the hangar this morning to help with the two-man task of putting the cowls back on, a job that traditionally signifies the end of the annual condition inspection and a return to flying status. I'm always a bit nervous about the first time flying after the annual - I was that way even before the days when I personally did a lot of the actual work like I do now. Now that I have a direct hand in inspection and repairs, it's even worse. I've been more nervous than ever this year, primarily due to the replacement of the gascolator, and to a lesser extent the work that was done on the carburetor since that part was done by my A&P.
With all of the trepidation in the air, I decided to get to the hangar well before Rick's expected arrival time to test run the engine again. I ran it last week after installing the EGT gauge, but about mid-week I got to thinking that I had concentrated almost completely on the readings on the gauge during that test and not so much about a full check-up of the engine. So, after that idea nagging at me for a few days, I ran it again this morning with a broader focus on the overall performance of the engine, and I'm glad I did! What I found is that because of plugging the hole in the side of the carb and/or having the carb removed and replaced, if I pull the throttle all the way back I no longer get to a 600 rpm idle. Now it goes down to between 200 and 300 rpm, then stalls. That, as I'm sure you can imagine, is by no means a desirable thing!
There are a couple of things that I think could be causing it. First, I think it's possible that plugging the hole in the carb has changed the fuel/air mixture at idle/low rpm, and without the extra air coming in through the hole it is now running rich at low rpm. I noticed that if I tried to throttle up from idle, the engine sputtered and carried on for a bit - it might have been choking on too much fuel. It's also possible that the excessively low idle indicates that the positioning and/or length of the throttle cable was changed as a result of the carb having been removed and replaced. That doesn't seem as likely, though.
In any event, I won't be putting the cowls back on until I've had a chance to have the A&P come take a look at it next week. Being grounded like this, of course, virtually guarantees beautiful weather for tomorrow.
You're welcome. Enjoy it.