What about the first part... what throttle were you running it at for the one minute ?  Was it always at mid to high ?  Or was it idling all the time (or most of the time) ?

Basically, if it overheated, we need to know which needle setting caused it. That is why these questions are important

Hi anwar. I understand.

1) The High speed needle...the one near fuel entrance into carb...it was at 2 1/2 turn anticlockwise, from fully closed, as recommended by factory setting. When i tried to lean it by tightening by 1/4th turn, next time the engine wouldnt start unless i brought it back to 2 1/4 ~ 2 1/2 turns.

2) The low speed needle was untouched on the day the engine started, but when it started stopping abruptly...on the 2nd day morning i tightened it by 10 degrees approx, not more.

3) no adjustment to idling screw.

the idle was at normal... i mean.... hands off the throttle

Sorry for asking the same question again.  So you started it, and left it in idle (hands off the throttle lever) for 1 minutes, and it died ?

yes anwarji...right...then i let it cool dwn nd tried to start it again..but the cord just came out n didnt rewind itself.

Ok, if heat related to needle settings is what caused this (I am not sure that it is), then the low needle may be too lean. 

Your oil content is questionable, it was only 12% when this happened, right ?  It was suggested earlier that you use more oil for the break-in phase.

no not 12% anwarji..methanol 82% & castor oil 18%

Ther 12% oil in this post http://www.rcindia.org/fuel-and-engines/help-on-fuel!!-2681/msg26413/#msg26413 confused me. 

A 10 degree turn from factory settings should not cause this, wonder if factory settings for low needle was indeed what it was started on.  I do feel bad about not suggesting the pinch test earlier, but then it was not clear from your messages at what throttle range you were testing it.

Is it better after cooling down, or do you have to change the rings (and possibly other parts) ?