I quote from the service manual.
"Clutch "Lock-up" inspection"
Perform this inspection to determine if the clutch is engaging fully and not slipping.
1. Warm the engine to normal operation temperature.
2. Connect a electrical tachometer to the engine.
3. Apply the rear brake as firm as possible.
4. Briefly open the throttle fully and note the maximum engine RPM sustained during the test.
Caution: do not apply full power for more than 10 seconds or damage to the clutch or engine may occur.
Std = 3500 rpm + - 300 rpm.
It's not supposed to "stall" just have a limited amount of slip which is expected but not more than that.
If it feels healthy it probabily it healthy.