Smoothing it out?

[DDO]

I would like to know what would make a good-running engine run smoother. I just thought it could be more even sounding, not that it is really off in any way. Suggestions?
We've traveled from posts "shake shake shake" to "valves revealed' and now I can post "it's all done": New valve, gaps adjusted, cover on, new manifold and flange placed, head on, thermostat cleaned, distributor serviced / checked, new plug wires, rotor, ring (EI), cap, plugs, and 2 oil changes... I even added a tach to help with settings. New carb earlier so I've been fiddling with its settings. Engine starts with a happy roar and runs great now, but starts with more difficulty when started a second time -- if that is a hint at anything. Can it be smoother, maybe something like "quiet purring"?

[CRUX]

I'm not sure if it has any relevance, but I used to have trouble starting a SECOND time as well. First cold start fired up first time everytime, second start I would have to open the throttle completely and with no choke. This seemed to be due to a leaky float valve.

[Al Schober]

You may be running rich (too much fuel). How do your spark plugs look?
The A4 should need choke when starting cold while a warm engine will restart well with no choke.
Personally, I liked the convenience of an adjustable main jet. Some folks don't like them as the orifice is an annulus rather than just a hole and therefore has a smaller dimension and tends to stop grit easier than an open hole with the same area.
The height of the float and the size of the main jet will also affect the fuel/air mixture.

[edwardc]

Easy starting when cold is a symptom of a too-rich mixture. An updraft carb should require a couple of tries when cold EVEN WITH THE CHOKE.

The fact that you need to open the throttle wide when warm is another symptom of a too-rich mixture.

Try increasing the idle air screw (counterclockwise) to increase air and lean out the mixture.

[JOHN COOKSON]

In my experience a properly tuned A4 needs brief full choke to start even when fully warmed up. Something to do with the updraft carburetor?

ex TRUE GRIT

[JOHN COOKSON]

SOME CALL IT NOISE - I CALL IT MUSIC

Noise implies malfunction.
I like to listen to the engine sounds to detect any problems. A somewhat subconscious thing. Works anywhere on the boat.

ex TRUE GRIT

[DDO]

Yes, I've been adjusting the mixture, trying to stay as lean as can be. Will look at plugs again after running awhile. The usual on this engine for years was first start required choke on, warmed up - didn't. The other day it was warm and took choke. That's really all that seems different, but I was hoping for a smoother sound than ever after all that work. (Of course no more shake-shake since the valve replacement and a way happier engine with all 4 cyl.)

[DDO]

Thought I'd add some words of follow-up. Fiddlin' with the carb and throttle adjustments did help, but only after disconnecting and reconnecting the throttle cable adjusted for more "throw" at the lever/knob -- one thing I didn't expect to have changed. I think she did "purr" today, so smooth and quiet. But it seems like the engine just needed to settle in after all the changes.