I'm sofa king we todd did, I didn't answer your question
Run one or two drywall screws into seal and pull it out. Wrap shaft with masking tape to protect seal, pack and lube seal with grease, install
Sudden catastrofic failure might. I wouldn't split the cases for that seal until I blew it out the third time
Clean case where seal goes with brake clean, pack and lube seal with grease, 3 bond on seal, wrap of masking tape on shaft to protect seal from rough shaft.
Did you take pilot jets out when you cleaned carbs? TORS or no? Carb top gaskets good? If no tors are idle screw holes sloppy? If stock carbs, is the little sight window tite? I had one fall out somewhere, don't know if while running or while it was waiting to be rebuilt. Check that you get good blue spark each and every time it sparks both sides, Ohm plug caps seperatly. Trim 1/4" off plug wire before installing cap.
You yourself admitted faulty comp test, highly doubt it would run with only 90lbs. Have you even done a proper plug chop? Have you tried adjusting idle with large screws on top of carbs? Can also try adjusting air screws. Needle only adjusts from just before half to about 3/4 throttle. If a proper plug chop reads good and you can live with no idle, I'd run it. Then during the three months off you can get a Clymers manual, don't know if download covers tuning as such, and read lots on the forum so you have a better idea of what you need to do and how to do it. Also you can pull the pipes and look into cylinders without having to get a head gasket.
JMHO, your results may, and will vary.
Doing a leakdown test first is hella easier, split cases, still gotta do it when done .
The Blasturd blew that seal out after half hour of hot laps on mini flat track, between slightly overfull tranny and plugged vent tube it popped right out.
What mods do you have? Do you realize that 220 is stock? Unless you're at way high elevation, I wouldn't go any lower. Maybe list ALL mods, ALL carb specs, plug type, and elevation.
If you filled it with 2s mix oil, I would fill and flush several times with ATF. Fill it, warm it up constantly working clutch, repeat, hoping you haven't smoked the clutches.
Unported 4mil w/head spacer, FMF Signature series, Vito's reeds, 950-1200', 310m, 27.5p, 1 1/2- 3/4 turns, middle clip.
Might be tad rich, but rather leave a horse or two in the barn and pistons in the holes.
JMHO, your results may, and will vary.
Also depends on if he's doing 1-6 pull on new plugs or is he just riding around and then pulling plugs. After reading lincs you'll know more. Even if DG aren't much more on power at least they weigh less