Randomly, this started happening Wednesday during my ride home. I opened the throttle up completely to pass a car and as soon as it hit 4k RPM it immediately started sputtering and would not accelerate past 4-4.5k RPM no matter what. This weekend I took a look and was able to repeat the problem easily. I noticed, however, that if the bike is in neutral (parked or not) it will rev up to 8k RPM or so, but also does the same thing where it starts sputtering out. It almost feels like someone came and installed a governor on the bike when I wasn't looking.
I tried a few things, but nothing helped:
1. Ran it with the gas cap open, just in case there was an issue venting.
2. Removed the pod filters and cleaned/re-oiled them - but also took her around the block WITHOUT the filters, no difference
3. Checked the battery voltage, that looked good (12.something, can't recall offhand, this was parked with the engine off)
Here's a video I took earlier, it's 4 minutes long but here's the interesting bits:
0:22: Parked, revs to about 5k RPM with throttle fully opened
0:42: Riding down the street, again limited to about 4-5K RPM
1:30: Pulled out onto the major street, 1st gear to 4k RPM no problem, 2nd gear to 5k RPM starts sputtering
2:55: While rolling along, I pulled in the clutch and was able to rev up to the red line without sputtering
3:20: Slowed down to lower gears and gunned it again, 3rd gear it sputtered at 5k RPM
3:40: Coasting into my drive way in neutral, and my dumb ass downshifted into 1st without the clutch. Whoops!
I just replaced the spark plugs a couple weeks ago with new ones (gapped them myself), the charging system was replaced last year with a TPE stator and new R/R. Not sure what to look for or test for aside from what I mentioned...any ideas?