Setup up front:
Yamaha Vino 2T (YJ50) minarelli horizontal engine
70cc BBK Athena sport aluminum
Yasuni Exhaust (derestricted)
Polini Air intake cone filter
brand new Dellorto 21mm carb
Initially I was running the stock carb (tiny), but even with a massive main jet it was running too lean so I bought a (stage 6) dellorto 21mm PHBG. Now I'm trying to dial in the carb. I've read through the "How to tune PHBG Carbs" guide and it's very useful, but I'm still running into problems with idle.
The default idle jet (50) seemed to rich so I switched to 45 and at the end of yesterday I finally got the idle dialed in. constant sound, responsive to throttle, but quick to return to idle. This was with the engine fully warmed up. Today when I start it (choke on) it has a much slower inconsistent idle and sounds like it's about to die. leave the choke on for 30 sec or so and when I turn the choke off it dies. start it, runs a few seconds, dies. then wont start. I check the plug and it's dry fouled. (of note, that's how the beginning of yesterday started before the engine was warmed up. I fouled an additional plug yesterday when I let it sit in idle for a few mins. I'm running out of spark plugs here)
To me this says that I'm probably still too rich? But I'm confused why it worked so well yesterday and struggled so hard today. Also why, if it is too rich, does it die when I turn the choke off? Seems like that would indicate it's too lean if taking out that extra fuel kills it. And lastly, is it normal for a 2T scooter to die if left in idle too long or should it be able to idle forever? (I've heard some dirt bike guys say their bikes foul plugs and die if left in idle on other forums).
Thanks in advance. If I'm saying something dumb feel free to point it out. I'm very new to scooter tuning.
(additionally, if it matters, I don't premix. I run the stock oil pump (not adjustable) and add 1 cap of full synthetic oil to a full tank on fill up)