Re: RDE-17 Johnson tuning issues

[David Stanton]

That does sound like a lean sneeze, but you had a fast idle going so maybe you were in an area where it was starting to transition from the low speed to the hi speed jet and none of the RDs run smooth at that throttle setting, especially when cold. I’d first try backing the throttle off a tad so you are definitely fully on the low speed needle, then turn it richer and see if the sneezing stops. At the point where sneezing just stops, turn the low speed needle 1/4 turn richer, but do this again with it fully warmed up for your best setting – when done this way, it may still sneeze while warming up unless you leave the choke part way on. Note that most of these RDs (25 to 40 HP), when properly adjusted, will still sneeze at an idle when first started up cold, but that should stop as it warms up. I have about a dozen of these motors, and so far have worked over 4 of them to good running condition. It doesn’t take much of an RPM increase from slow idle to get some gas going in the high speed venturi, and if you have that happening, you will never get a good low speed needle setting. I also put a boss gasket in all of them if they didn’t have one – and, as has been mentioned, the hi speed adjustment has to be made richer. I’m sure you already know that the low speed gas goes up a passage on the side of the carb bowl to the low speed needle above the bowl – spraying carb cleaner through this passage insures it is unobstructed.
Dave