Because of the intimate contact between the manifolds it's common to have percolation problems. If the weight on your heat riser is in this position with the engine warm you're OK, or at least as OK as you're going to get with that manifold set-up. If it's rotated clockwise from that it's allowing excessive heat to cook the carburetor. What happens when you shut the vehicle off hot is the fuel in the bowl boils out and fills the intake runners with fuel rich vapor. When you try to restart it's like trying to start a hot engine with the choke on. My hot restart ritual is a bit different from truckernix's in that I don't touch the gas pedal, I arch my foot over it and press the starter pedal only until it catches. My reasoning is I don't want to put any more fuel into an already rich environment. I understand his too in that with the throttle plate open it'll pull the rich mixture out more quickly. Experiment until you find what works for you but you first need to make sure your heat riser isn't stuck in the wrong position.

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