Hi Shunmuga, Nice to know that you also own a 800. I think your clutch is slipping. See, what happens that when you leave the clutch, the clutch plate comes in contact with the flywheel and starts rotating. So far so so good.
Now in your case, the clutch comes in contact with flywheel but is not rotating at same rpm as of flywheel. This may happen due to clutch slippage. The clutch comes in contact with flywheel but flywheel rubs over the clutch plate and can't get attached to it due to damaged grooves on the clutch plate resulting in rubbing kind of effect and you feel loss of power.
Refer to the image below, the circular mark on the clutch plate is formed due to slippage of clutch.
35k kms is low for clutch to go bad, Do you or any one else who drive the car rides the clutch? (Foot on clutch while driving)
This prob can happen also if your clutch cable is not properly adjusted.
Do this simple test-
Park the car in open (Some space ahead of the car).
Start the car, slot into first gear, Pull the hand brake.
Now leave the clutch slowly, If the clutch is normal, car will shudder and engine ll go off when you have left about half the clutch or so.
If it doesn't go off above half clutch also, your clutch is slipping and clutch needs changing. BTW
does your car shudders when you leave the clutch in first gear (Normal driving)?
Does the engine feels stresses when you cross a hump in second gear?
After this clutch overhaul, my car manages a speed breaker even in 3rd gear (Wont advice third gear for speed breakers though, but the engine no more feels stressed).
If at all you need a clutch overhaul, change the following things-
Fly wheel (Along with the small bearing)
Many service centres ignore the cable, but its necessary to change it. Mine also ignored, and my clutch pedal developed some noise, so had to change afterwards.