This is a GREAT thread!
from biknut
"It's not all love and roses though. I have yet to mess with the low speed much yet. Right now it starts Ok, Idles Ok, and accelerates OK, but it has a nasty little spot right off idle. If you give more throttle it goes away. I think it 4 strokes there too."
Try the small square filed at the down-stream side of the slide to let in a bit more air during the transition from idle in through mid range.
from brandon's WILD phone video!!! (I ain't young any more!) ..at mid range there was a lot of 'burbling' at mid range... 4 stroking... needle is wrong.
Same thing as biknut... profile of the needle is probably incorrect. Try filing a small square out of the very bottom of the slide with a needle file... I once read it somewhere I can no longer recall... maybe Gordon Jennings, but I dunno...
Way back when I was tuning yamaha's with mikuni carbs and expansion chambers.
...Driving the screwdriver into the 'pipes' inside the muffler to open them up just kinda changed everything! Time to re-tune... again! Make a change to the pipe, time to revisit the main jet. Then, the other settings.
IMO this thread shows, more than anything, that perseverance and going through the process step by step will get results in the end.
...and then as the engine gets broken in, U gonna have to go through it all over again ! LoL
Basically, these engines are SO SMALL, and we are expecting quite a lot from them. Things would be far simpler with a 5hp or better 4 cycle with flywheel mass to it. There's really no substitute for cubic inches!
..but that is a different game..
Best
rc