Oil in bike gets dried up very soon.?

If you are not seeing any puddles of oil under the bike it has to be blowing by the piston rings or have a burnt valve that is allowing it to get into your piston chamber. The only way to fix these items is to remove the engine and rebuild it.

Additional - Most synthetic oils will not smoke when burned in the piston chamber.

Riding in the rain - there are those who do, those who don't, and those who won't no matter what. I ride in all weather, so I can give you a few tips. Tires - you should have at least 1/3 tread to be comfortable. Not to the wear bars. Tires do become harder with age, if they are very old then replace them. On the road - things are different during rain than they are during sunny weather. Visiblity is reduced, not just for you, but also for every other driver. You become harder to see, and may not even be expected. Drivers do not see what they don't expect, unless they see it too late. Braking distance is increased, just as in any other vehicle. After I go through a puddle, I tap the brakes and give them a wipe (old habit). Many of us were taught to divide the travel lane into thirds, these being the right lane, left lane, and the "grease strip" in the center. At the beginning of a rain, the oils etc. that are trapped in the imperfections in the surface will rise to the top. Travelling during the first 20 minutes to 1/2 hour is not usually recommended. The center grease strip is one of the worst places to ride in rain. Other things that become slick: painted lines, manhole covers, railroad tracks. If you must cross any of these, try to cross at a 90 degree angle, or as best as you can get to it.

Check for any leakage in the engine oil chamber.

If you are using synthetic oil, they will vaporize with engine over heating.