XJ750 Midnight Maxim no power

I have a 1983 Yamaha XJ750 Midnight Maxim that tends to be sluggish on idle and has recently lost power during ride. To take off I have to rev up to at least 4rpm and let off the clutch slowly. Once running it will jerk forward for a second as I'm driving and then just back to how it was. The ride feels as if I had my brake on but I've checked them and they work perfectly fine. The bike was stopped for about 6 years when I got it from my dad and I've had to clean out the carburetors at least a dozen times to get them fully clean. I did replace the fuel injector needles and main gaskets on them. Also I've put in a fresh set of spark plugs along with a much needed oil change. New fuel filter and petcock rebuild kit, tank was vigorously cleaned out and still has the same air filter. It looks to be in good shape so I decided to leave it. I do have minor oil leak from the left side (from front of bike) but I keep up with it religiously. I have a misfiring cylinder(first from left), but the piston moves freely and I have good spark. This is my first bike and dont have much money to take it to a shop. Also it's my only transportation. I've tried going through here to find a fix, but I havent found my problem specifically. Any help would be great. Thank you in advance.