Its a strange issue.... I have an older Honda with a cable clutch running for it, and i swapped the engine out around last October or so.... Checked the clutch, and it all looked good. Teeth were all there and looking good, and the disc had plenty of friction material on it.

And when i drive it, it drives just fine. No slippage, chattering, etc; its great. Except for when i want to take my engine above 6500rpms. For some reason, whenever i do this, and try to shift, my clutch pedal STICKs to the floor until the engine decels to ~5000rpm or below, then begins acting normal again. What could this be? (its a stock clutch with ~150,000mi on it btw)