LT80 not revving out

I have a '99 or so LT80, pretty well taken care of. I love it, but it doesn't like to rev out and get full speed, it seems like it hits about 1/2 of it's top speed and starts hesitating, or something very similar sounding to hesitation. Basically stays at that speed, doesn't go any faster, but it's too slow to actually be hitting the rev limiter, I think, especially considering I've got the 428 re-gear kit on it (supposedly good for another 5 mph).

Right now, I'd estimate the speed around 15 to 20 mph, way slower than a stock LT will supposedly do (30 mph) and WAY slower than my regearing kit is supposed to make it go (34-35 mph). I have cleaned the carb, adjusted needle clip, cleaned jets, nothing seems to help. The plug looks great, a tan color and not many deposits, so I am totally lost as to what's wrong.

Any help at all would be greatly appreciated.

Oh, before I forget, it's got an FMF Fatty pipe on it. That's the extent of the engine mods it's got.

Check the front clutches on the machine.

I'd like to know the compression.
I agree the clutchs need inspected and serviced. The grease gets hard as a rock and limits the roller travel. From the rollers working in a lilited fashion, the roller hub and the plate that covers the rollers are usually grooved/wore uneven/made a big divot/etc.
At your Zuki dealer the parts including new rollers should be approx $65. If needed.

FYI: no rev limiter. :)

Did this happen after the pipe was installed or was it running fine at one point w/the FMF?