Am not happy to say it here that i still could'nt stand on a bicycle. Even while in my secondary school days my friends make jest of me. There was an occasion they helped me with the bicycle and left me by myself on it. I guess you can understand what happened next. (A great fall). I have heard about the gyroscopic effect before probably in my physics class but never connect it with same principle for bicycle.

Stability was my problem then. So i think i will agree with the last paragraph and the mass distribution effect.

I think the castor effect also explain better. Thanks for this information @greenrun