Oof, my bad I'm also just realizing this is in the 250CC and up section, and it should be in smaller twins and I can't figure out how to delete it. My bad, my bad!
I attempted to, but it got held and then... deleted? by mods. I suppose I can re-post it now since it's been a few days, just kinda dumb, I can't figure out how to delete this thread so it's always gonna be a duplicate.I'd advise that you create a new post in the proper section as the engines in the CB200 are different.
Thanks for all the info! I believe the carb floats were initially set 2-3mm too high because whoever set them previously did it from the edge of the case (rather than the gasket mating surface with gasket removed) so I lowered them each about 2mm. I've been contemplating swapping the carbs out for replicas for a while- I might ultimately have to do that.As long as the needle seat screws in and the washer under it remains flat and flush, it should be good and not leak. A float level set too high can still cause gas to leak through in small amounts even if the seat seams to be sealed properly. I had the same issue of gas in the oil (and overflow from the carb), and the float was indeed set a little too high (even though it was set to spec), so lowering it slightly fixed the problem for me. Be sure to set it properly, it's from the gasket mating surface (with gasket removed) and not the carb body lip.
Even if a small amount was allowed down the cylinder walls, it should be diluted enough to not foul the oil. I think you have an overflow issue from the carbs while the bike sits that needs to be fixed, aka a float level set a little too high possibly.
It's very tough to diagnose these problems as even the smallest thing can cause it. I spent nearly a year trying to fix this issue along with a host of other problems with mine. I ended up swapping carbs for Chinese replicas (brand name OEM/STD or OEMSTD or Wincycles) for $70 and my issues are fixed. Took a little modification and reuse of OEM carb parts but I am back in the game.