Having a hard time getting the float valve to function on my Model 85.  My bike uses a 27mm Amal Concentric.  The float and float needle look healthy and the seat looks clean, but fuel gushes into the intake duct and also out the tickler port.  I can hear nothing when I shake the plastic float, and there are no pronounced "steps" in the float needle.  Can someone suggest other things I can check?  Anyone run into this before?

The plastic float needle in those carbies does not give a reliable seal and can become roughened where they touch the seat. To see the roughness I need to use a magnifying glass and good lighting. However while that can cause fuel to fill the crankcase overnight if the fuel tap is left turned on, it will only be a tiny trickle, not a gush, and if the tank tap doesn't pass, is generally not an issue.

Maybe test yours with the float bowl removed and you holding the float up when you turn on the fuel tap, to see if that reveals what is going on.

My first thought is that perhaps your tickler is touching your float

Thanks for your suggestions, feetupfun.  This is for sure a gush and not a trickle.  The stem of the tickler is retracting properly, and I've triple-checked that there is no interference of the float swinging freely because of the bowl gasket or any other hindrance.  The previous owner left the bike sitting in a field for approximately 40 years, and the float bowl was FULL of dirt and green/white crystals.  I have to wonder if the float needle was distorted in those years by the temperature extremes (-24 to 39 deg C in my area) and the force of the crystal growth.  Does anyone sell a rubber-tipped float needle for this carb?

pretty sure the standard needle nowadays is rubber-tipped https://amalcarb.co.uk/shop

GREATLY appreciate your assistance, feetupfun.