So my father-in-law has a '91 K1 which he bought several years ago. He's letting me take it over because, while he loves the bike, it doesn't really fit him (he's more of a cruiser with all the bells and whistles type guy). The bike sat for a year, covered, but not really garaged, before I got it running (new gas, new battery). I know it has had maintenance by a local import bike shop, though I don't know the full service record.
After ~100 mile ride the other day it started bogging down. It would be running well, then suddenly the bike would start dropping RPMs and the throttle's responsive ceiling would get lower and lower. I'd pull over, turn it off and sit for 5-10 minutes. Then I'd start it up and it'd run fine for several miles, before I'd have too do the same process again. If I didn't wait long enough it would be hard to start as if it was very cold without enough choke.
My first thought was overheating as the symptoms were similar to when my Trans Am would overheat. But I was able to get the bike to cool down and the problem persisted. The next time I rode it, everything was fine though I only went ~20 miles. Since getting it running it's probably gone about 300 miles and just ticked over 10k on the odometer. My current hypothesis is junk in the fuel system is causing problems. I'm hoping the gurus here have some advice.