Need help: rough idle and dies when accelerating

Update in case anybody can help me troubleshoot this:
last night I started by draining the carbs bowls: fuel was crystal clean. Then I opened the carbs, remove the diaphragms and inspected the jets: they look clean. I also made sure that all the carb vents were clear and they were. Then I removed the crankcase vent hose, that was clean too. I looked into the airbox and there was no fuel or fuel residue. I also checked if the fuel feeds properly from the tank and it does, an inline fuel filter is clean. Spark was present on both plugs. I cleaned the plugs anyway.
This morning I start the bike and even though it was running slightly better it still has no power. I realize that the right side is cold and the bike is running on one cylinder. Check for spark again, the spark is present on both plugs. They do not look fouled. I let the bike idle for 20 min or so and I ride it around the block, I can rev it and it does bog and dies like the day before but it is definitely still running only on the left cylinder. After stopping I noticed a little smoke coming from the right exhaust and black oil starts dripping from the right exhaust where the two exhausts connect underneath the bike.
At this point, I assume I somehow blew a valve seal or a piston ring: I inspect the plug again but it is not covered with oil, it actually smells like gas (see attached picture)!
I am definitely confused here, I cannot believe this all started from accidentally plugging shut the carburetor vents.
I am going to do a compression test tonight, any advice is extremely welcome. I was so proud of how the bike was running after the carb and electrical work I did and now I am really frustrated. Thanks guys.

I agree with the compression test. Based on your description I wonder if you're getting fuel from the bowl to the cylinder. You say the plug smelled like gas but wasn't wet? Unusual if the cylinder is not hot. Could you have put a strain on the carbs when you pinched those hoses? Sounds like you aren't getting fuel to the right cylinder. Just a guess but you never know. Good luck and don't let it get you down. You'll figure it out. Later

PLEASE add your bike's year and exact model to your signature line! That will help others help you. For example - you may simply have the wrong heat range spark plugs installed, but without knowing which model bike you have there' s no way to tell. Ed

Maybe try a new plug .... some of us have fouled one good enough to not come back.

20 minutes is a painfully long time to idle an air cooled bike. Please consider running it for a shorter time while troubleshooting.

Markovich wrote: I agree with the compression test. Based on your description I wonder if you're getting fuel from the bowl to the cylinder. You say the plug smelled like gas but wasn't wet? Unusual if the cylinder is not hot. Could you have put a strain on the carbs when you pinched those hoses? Sounds like you aren't getting fuel to the right cylinder. Just a guess but you never know. Good luck and don't let it get you down. You'll figure it out. Later

I disassembled the carbs and checked if I caused any damage to the diaphragm or the floats, everything seems ok. They're clean, needles slide up and down nicely, floats fork and fuel level in the bowls is perfect. I also re-checked the airbox and didn't find anything suggesting fuel overflow into the box. Checked for spark, even swapped the plugs and the right cylinder is still colder than the left one. I changed the oil and it definitely was polluted with gas. Finally, I ran the compression test: cold, no lubrification, left cyl tested at 100 PSI, right cyl at 102.5. Hot, with a little oil on the heads both cylinders tested at 90 PSI... a little low uh?
Bike fires up and idles fine, when I accelerate reves go down for a second then come back up and white smoke can be seen coming out the right exhaust. The bike seems to rev better with no air filter on, but still, it's not rideable one can definitely notice the lack of power when releasing the clutch. All this is suggesting me that I need a top end job. It is just so confusing to mee that all this was triggered by plugging the carb vents for a few minutes...