If you'd like to just read the problem and not the story, please see the last few lines.
Alright, here I am, on a nice but slightly warm day cruising along in 3rd or 4th gear at about 6500rpm (after bump-starting my bike, which is another problem altogether). Out of nowhere, I get some pretty stong engine braking, like I instantly cut off the throttle but even more, and my rpms drop down to roughly 3500. I pull in the clutch and coast her in neutral to the parking lot up ahead.
So my bike finally dies, and when the key is in the 'on' position, none of the lights that should come on do. Battery not properly connect? So I bust out the crap-ola tool kit to take a look-see, and everything seems to be in order. I use a zipper cover thingy off of my jacket and tie down the clutch. With my right hand I hold onto the throttle, ready to blip it when I do this next step. That is, hold onto a pair of pliers from the aforementioned crap-ola tool kit with the book I was returning to the library (A Clockwork Orange) and bridge the gap there. I do this, and get sparks, meaning my battery is good to go. Strange, I think to myself. Anyways, it didn't start, and I bump started it (I'm an expert at this, I bet I've done it almost 100 times on this bike). I nurse her home at 3300rpm in first gear (which is 10 mph, by the way), which luckily is only about two miles away.
Well, as I near the downhill portion of my journey, I kick her back into neutral and just give enough gas to keep her alive. Here's where it gets interesting. As I'm getting ready to take this downhill turn, I throw on a little rear brake action to slow me down. Right as I step on it, my rpms jump up. An anamoly, I think to myself and head on home. I did some more testing and it turns out that any time I hit my rear (not front) brake, the rpms go anywhere I want them to. I tried unhooking the little actuator thing from the rear brake, and lo and behold, I find myself once again limited to ~3500rpm (even when depressing rear brake). I double checked after replacing these wires, and the rpms jump exactly when the brake light comes on.
I am riding a bicycle to work tomorrow.
For those who skipped the story: My rpms won't go above roughly 3500rpm, UNLESS I depress the rear brake. I have determined that the action of the rear brake light coming on is allowing things to work as they should.