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Old 09-20-2020, 06:25 AM
scard's Avatar
scard scard is offline
Join Date: Jun 2005
Location: Cedar Park, TX
Posts: 3,197

Originally Posted by Emery View Post
I will add one more note to close off this post. I have finally given the engine a good run with the carb reassembled with all original parts.

I did not adjust anything, and somehow I no longer have the way too rich condition and roughness that required so much leaning.

While the carb was apart, I blew out a few orrifices, reused the original float, and did not detect any wear in the float fulcrum pin to float area.

With the original problem, I did not have an air filter in the fab airbox.

I'm getting a static full throttle rpm of 2200 rpm and it increases by maybe 20 rpm if I lean.

All in all I am happy with my new results, but not sure what the original problem was.
Thanks for the suggestions.
No air filter? I think that is a critical piece of the puzzle.
Scott Card
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RV-9A N4822C flying 2200+hrs. / Cedar Park, TX
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Old 09-20-2020, 02:23 PM
Emery Emery is offline
Join Date: Jan 2018
Location: Whitehorse
Posts: 74
Default No air filter

OK. Enlighten me. It was the only thing that I added that was not in my first problem test.

I have run other engines without an airfilter while working on them seemingly without much difference with or without an air filter.

If this Lycoming is sensitive this way, than I have learned something.

Can anybody confirm this? Thanks
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Old 09-21-2020, 02:55 AM
PCHunt PCHunt is offline
Join Date: Feb 2007
Location: San Diego, CA
Posts: 1,714
Default FAB not installed

I chased a bad idle and a rough running O-320 carb engine, and found that running it without the FAB and filter installed caused most of the issues. As soon as I installed the FAB and filter, the engine ran "sweet", and only needed minor idle mixture and idle speed adjustments.

The engine ran well at high power, but idled very poorly. I can only assume that the airflow past the carb was disrupted enough to cause the issues. I also had a left mag issue that contributed to the problem.

NB: I was running the engine cowl off, with a bare carb. No FAB installed, no filter installed. Reinstalling both fixed the issue, even with cowl off.

Not sure if this was your issue................
Pete Hunt, [San Diego] VAF #1069
RV-6, RV-6A, T-6G

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Last edited by PCHunt : 09-21-2020 at 03:06 AM. Reason: Corrected error
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