I don’t know much about RBM’s. My 1922 Model A starts best with the mixing valve turned out 1/2 – 5/8 turns. The poppet valve happens to be set around 2/3’s of a turn, but I don’t think that’s a big deal. I set mine while it was running on the boat and then left it alone. I’m currently working through some magneto issues so I don’t have much running time on the motor.