It's been a long haul, but finally we have something that runs. There are a few problems. For one thing, it smokes. For another, it heats up rather rapidly. Hopefully, these things will improve with running. The real Merlin prototype was developed by the time-tested method of running it until something broke, fixing that, and repeating the procedure until nothing broke. Hopefully, nothing will break on the Quarter Scale Merlin (wishful thinking!), and all that will be necessary is to 'break it in'.
About the only serious problem so far is that the carburetor intake has to be mostly blocked off for the engine to run. Obviously, that isn't holding the engine back much, at least at low speeds. The carburetor design uses parts from a Honda GX120 carb, adapted to the necessary 'up-draft' configuration. The carb is two-barrel, like the real Merlin's, but each barrel has its own throttle control, and only one throttle has been used so far. The throttle bore is 16mm, and the venturi is 11.5 mm. Those dimensions were arrived at after a great deal of study, but unfortunately, information regarding carburetors for small V-12s is somewhat lacking. Perhaps playing with the jet sizes will help, and/or a smaller venturi size.