Trouble starting/loss of power
I honestly have no idea which area this is going to fall under, so I'm tossing it out here (some of it is electrical I suppose, but I'm not sure the entire thing will fall under that classification). I've got a 1991, which I bought about 3 years ago. I've never had a battery last more than one season, but for the first two years I was stupid and didn't put the battery on a tender during the winter so I figured that was the issue. Had it on a tender all winter this past season, got it out of storage and it fired up pretty quick. Rode it for a month or so with no issues at all. Within the past month or so, it's been having trouble starting. It's working to turn over but it just won't fire up at first. It usually fires up after a couple tries (I've found it starts better if I leave the choke closed, twist the throttle once or twice while starting, then open up the choke after it fires up). A week or so ago, the battery completely died while I was at work. I shoved it down the hill and pop-started it, let it run for a few minutes, then headed home. It tried to die after a minute at the first stop light; I revved the engine a bit and it was OK. Getting on to the highway, it suddenly felt completely sluggish, like the engine was running but there was no power. I couldn't get over 50 mph. Was about to pull over when suddenly it sprang to life and everything was fine. I have about 12-15 miles of interstate on the way home, and it ran that with no problem at all. Get off the interstate, hit a stop light. No issues. Go half a mile, and sluggish again; this time I can't get it over 35 mph. Just as I was pulling over, it came back again and I was able to ride the last few miles home without incident.
I've had a ton of possible issues suggested to me, from spark plugs to bad battery to bad alternator to gummed up fuel lines. The feel I get from it is that the engine is running fine, but isn't providing any power. Problem is, I know next to nothing about these things so I have no idea what those symptoms would indicate. Money is tight right now so I'd really like to avoid trying 5 different things before I find the real issue. Any help you guys can provide would be much appreciated!