Talked a bit about this moped in another post but I'm gonna lay out everything I did here in one place --
I got a Moby 7 from a friend which ran after I cleaned out the carb (Sha 15.15) but was having some issues where sometimes it would work fine, sometimes it would only work with the choke on, and sometimes it would just die. I decided to clean the whole thing out after reading Fred's Guide, I took apart the engine, changed seals, bearings, gaskets, motor mounts, throttle cable, decomp cable and reassembled. It started up, but I was experiencing the same issue (needed the choke to run most of the time, except randomly it would work fine).
I thought "it's either not getting fuel or getting too much air". I sprayed starter fluid around anywhere that might leak and it didn't affect it, so I thought it's a fuel issue. Thinking "the jet looks clean but maybe it's clogged or the previous owner picked the wrong size, I stuck a 65 jet that I had just bought instead of the old 63 jet -- this seems to have fixed it! I rode it around maybe 1/2 a mile that night and 1/2 a mile one more other time but it's been raining all week so that's it.
Cue today: it's sunny and I want to go for a ride! Moped starts right up, everything seems good. After idling a while I turn it off to clean it up a bit (tighten loose throttle, shorten the new gas line that I made too long) and after that I try to start it and it won't start... I try to check if I have spark -- I can't see one (in the sun?) But my multimeter seems to be picking up a change on the plug once per rotation. I do notice that the plug is black and oily -- I clean the plug with a rag and stick it back in and it works! For 15 seconds, then it dies again, I pull the plug and it's oily.
Could my upjetting by 2 cause this? or bad oil/gas mix? Did I correctly troubleshoot my "choke" problem or did I just create a new problem instead. Maybe the spark is a red herring and something is changing when I leave it alone to cool down...
Starting to get frustrated, I wanna ride while it's 70 and sunny 🙄