This one has got me stumped...
I just completed a rebuild of this engine (the same engine as in my other post with the recoil issue). The first time I start these engines up I always install a "Vacu-Jet" carb/tank assembly due to the simplicity of their design and less things that could go wrong as compared to the "Pulsa-Jet" carb/tank that this engine originally came with. The engine starts, idles, and runs absolutely perfect. So far, so good...
Then I installed the original "Pulsa-Jet" carb/tank that I had thoroughly cleaned and rebuilt (I have my system/technique down pretty good after all these years), and adjusted the valve/jet to 1 1/2 turns out which is the default setting While it STARTS fine, once you apply some throttle it sputters and puffs out black smoke every time. At full speed (3600 RPM), however, it runs fine. Drop it back to idle again and then apply throttle you get sputtering and black smoke every time. I tried adjusting the valve/jet turning it in (which helps some). Once I get it adjusted down to only about 1/3 to 1/2 turn out the sputtering and black smoke stop, but it now will not reach full 3600 rpm.
This is the first time I've ever had one of these engines displaying a RICH condition- I've had a LEAN condition a few times before and eventually been able to diagnose and correct it. The engine seems to "load up" to a richer and richer condition the longer you let it idle, which eventually makes it idle slower and very rough. I have tried changing the valve/jet and the brass screw-in seat. Also, I inspected the 2 "cat's eyes" ports under the brass seat and they do not look enlarged. I completely cleaned the carb and passageways a second time and installed another (new) diaphragm.I am out of options here that I see. Kind of a shame if this carb is a "dud" and i cannot use it as it is in beautiful (cosmetic) shape.
Does anybody have any ideas?
Michael