Now arriving home from some pretty awesome power pulls on country highway, w/o pinging or hesitation I decided to track down some post shut down percolation which puts a bit of raw fuel on the bottom outside of the carb, every time, all weather about 15 minutes after shutdown.
It seems modern gas boils off around 100 degrees F. Not a problem for fuel injection which is pressurized to 40 odd lbs and no place for it to boil.
But I wanted to verify bowl fuel temps from shutdown to about 30 minutes out with the hood closed. Its 45 degrees out today. So if the carb perks and the fuel temp is high, I'll know I need to further insulate the carb, essentially a barricade between the manifold and bowl to help with heat soaking after shutting down.
Off we go, under the hood and immediately dunked in my temp probe thru the open slit in the top of the carb and slapped the air cleaner on and closed the hood.
Initial temp of the fuel in the bowl (carb sits on an insulating spacer, so we know now this is in fact a radiant heat issue) and shows the following temp about 5 minutes post shutdown.
Within about 15 minutes the fuel in the bowl has risen in temp considerably......at this point I lifted the hood for a bout the sixth time and noticed the first bit of wetting out on the outside of the carb....basically, fuel expansion and potential perking. (Yep, the float is set perfect at 39mm up, 50mm down.....)
From here things slowed down...long about 30 minutes the maximum temperature of fuel in the bowl was reached....on a 40 degree day.......
As you can see, add in summer temps and post shutdown, even with the hood open can lead to expansion and percolation.
I will probably first try lowering the float a smidge. But that alters the performance of the carb so have to be careful.
For sure, I'll be seeking out and adding insulation to the fuel lines and putting some form of heat blanket on top of the manifold to further protect the carb from excessive radiated heat.
In all, another 30 minutes well spent.