Sorry for the ambiguity here.. I'm not sure what the issue is with my bike. I have a bunch of symptoms and my hypothesis is that it's a cascading failure and I'm just seeing a bunch of effects down the line.
So here goes: I recently bought the bike, the previous owner mentioned that they were concerned with a fuel line and that they had replaced the stator/rectifier recently.
Almost every time I rode the bike the battery would die. It was an old battery so I replaced it today with a lithium battery, checked the voltage before the ride (13.22V), after about an hour of riding (13.01V) and again when I got home (13.16V).
After seeing it dip from .22 to .01, I worried that it wasn't charging correctly and rode at higher RPM - 7k RPM or so as opposed to 3-6k RPM (the bike is LOUD).
So that may have helped it charge but that does seem like it should be charging at lower RPM - the previous owner said 3k RPM should be enough for it to charge. When the bike is off if I check the voltage it's not dropping by itself.
After riding for about an hour, the bike starts behaving oddly. When coming to a stop, the RPM tends to roam a bit, like it's struggling to breathe. Also, starting from that stop tends to be difficult, feels like a slipping clutch and I have to really give 'er to get it going, but once it's going it's fine. This is usually followed by a dying battery if I don't get home quickly. Also when this behaviour starts, if I shut the bike down and let it sit for 15 minutes or so, everything goes back to normal and it seems fine. I don't think it's related to temperature directly, although maybe when the temp goes up and the fans kick on there's more power draw.
One final thing: it doesn't feel like a 1000cc bike. It feels more like a 600, but when I first fire it up there's plenty of power and it seems to dissipate as a ride. I recently went for a longer ride and at some point it sounded like only two cylinders were firing, and I could barely keep up with my buddy's old CBR 600.
So: coils, CDI, stator/rectifier/regulator, fuel/air? I really don't know where to begin.
EDIT 1: okay, I checked all three phases of the stator, all output ~12-15VAC (I don't remember exactly) at idle, and ~50VAC at 5k RPM. The connector is discoloured though (slight browning around the contacts). I plugged it back in, pulled the headlight fuse to reduce load and restarted the bike to find the battery charging at idle (~1900rpm). I got the headlight fuse back in, let the bike warm up to 105C and heard the fan kick on, and even with all of that the battery still was able to hold exactly 13.56VDC. So in other words, I'm back to square 1. Either it was a connector issue and messing around with it cleared it up, or this condition only comes up after riding for like 1-2 hours, which I suspect since it always seems to start strong. What do I need to look at next?
EDIT 2: I've ridden a bunch today. I checked voltage before and after cold start, then at each stop right before getting back on to ride I'm checking the voltage before/after starting. Here's the results. The bike still feels under-powered but I think that's a separate issue - I think the charging issue is resolved and for now I'm going to attribute it to a connection issue that I inadvertently fixed by pulling things apart and putting them back together. These voltage readings seem quite healthy.. closing the question, I'll open a new one later if it continues to be an issue.
13.21 cold, pre-start 13.50 cold idle 13.26 stop 1 cold 13.45 stop 1 idle @ 88˚C 13.4x stop 2 cold 13.5x stop 2 start @ ?
EDIT 3: Thought everything was fine, but my last stop of the day was a coffee shop for two hours or so. Come back out and... bike doesn't start. 9.4v on the batt.
Jump start, go home, pull it apart and test the R/R and stator again. Everything appears fine except the connector where the stator meets the R/R is getting really hot. Some Fireblade owners say is best to solder the wires rather than use the connector. New stator on the way.