Welcome to the forum.
Go to the home page, and download the appropriate service manual for your bike. It should help you with diagnosis and treatment.
On to the more relevant issue:
If you've had oil in there that turned to glop, it's entirely possible the whole engine/transmission is just plain gummed up. You have a couple of options. Get about a gallon of kerosene, drain the existing oil, replace it with kerosene, and run it for about 5 minutes or so until the engine gets warm. Drain the kerosene, replace the oil filter, and put in fresh oil. Kerosene will dissolve a lot of the crud inside the engine. If it comes out nice and black, it's done its job. The other alternative is to get something similar to Rislone engine crankcase cleaner (usually sold in quarts). Drain about a quart of your existing oil, replace it with the Rislone, and run for about 5 minutes. Drain it all out, replace the filter, and refill with fresh oil.
I would suggest running through the gears while this internal cleaning is going on, but I realize the engine won't shift properly at this time. Hopefully, when all the gunk is out of the engine, things will work a bit better.
Good luck. If anyone else thinks this is a bad idea, please chime in. Joel, you may want to wait a couple of days before trying this, just in case my reasoning is way off the wall.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.