Itinerant Air-Cooled

asiab3 wrote: There is also a new needle valve in the carb.

I'm beginning to think those "needle valves" should be replaced at a regular interval of, say, every year or two. Not too long ago I disassembled 5 valves
I happened to have, and found: one, probably from some rebuild kit, had a ball bearing tip instead of a needle; one with non-Solex markings, but otherwise
of identical construction, in good shape; and three Solex valves with a very pronounced wear ring where the "needle" met the seat.

The "needle" is actually an approx. 60 deg. cone that seats on a fairly narrow chamfer at the valve orifice.

While those worn valves probably do an OK job of regulating fuel bowl level underway, they may well leak enough at hot shutdown or when subjected to
fuel tank gravity pressure to cause problems.

I have speculated wildly that there is a variation in needle valve quality going around. It would be interesting to test somehow, though I don't know how we'd do it.

asiab3 wrote:I have speculated wildly that there is a variation in needle valve quality going around. It would be interesting to test somehow, though I don't know how we'd do it.

Consider this:

I have only filled my crankcase with gasoline when I installed new needle valves and went to bed
*without starting the engine*.

Fuel pressure, paradoxically, helps the valves close. Fuel rushing in will push the float up against the needle valve with some verve.
Lack of pressure can allow fuel to trickle in. You can park a car, fuel evaporates, float drops, fuel is allowed to trickle in due to heat soak or full gas tank, and the needle valve will never be pushed enough to close.

The only crankcase floods I run into out in the itinerary is due to contamination.

You can test a needle valve by blowing into the nipple and pressing lightly on the tip. I suggest exercising a new needle valve in this manner, but with more closing pressure to help "lap" it. Blow hard all the while, press/release/press/release/press/release, etc.
Colin