A correctly adjusted mehran engine requires you to pull the choke when starting a cold engine, (I believe you are starting on petrol), It is then required to push it back halfway and let the engine idle fast till it warms up so it does not shake - then push it back in (it can be pushed back if you are on constant movement too with engine partially cold).The sound can also be tyres - swap back to front, and the sound can also be from rear bearings. Check them all, For oil leaks - Get a new copper washer of your required size, smooth it out on a file, ask a denter to heat it up till it glows orange and quench it in cold water. Drain out all oil into a clean pan. remove old washer from bolt, clean bolt threads and install new washer, tighten the bolt into the sump loosen then tighten again. This causes the soft copper washer to seal to the sump. Fill the oil back into engine.Keep such washers as spares with you so you can change them everytime you get an oil change, do not throw away the old copper washer, its reusable - just reheat till glowing and quench in water.