^the proper way of checking the oil would be to start the engine and warm the oil up then turn it off and let it rest for 3min or so, then read the level, the reason behind this method is that the volume changes with respect to temperature therefore oil volume is measured b/w 23 to 30 degrees
did u changed the oil filter as well? if so then u'll need to refill atleast 250ml of oil in order to accommodate the new oil filter. This happened to me too when i changed the oil filter and filled the 1 litre in, the oil level was normal but when i drove the bike then the oil level dropped below "low", i searched the net and found that it is quite normal and u need some extra oil when u change the oil filter
if thats not the case than u might have some problem with ur engine!!