Ideally a production line is perfectly balanced and most efficient when all the stages have been allocated an equal amount of task times, but realistically this situation is almost impossible for a practical problem. For such an ideal situation, the just-in-time (pull system) production system holds no inventory in between the stages, such that the production process is just-in-time. The stage operation limes are random variables and the mean of each operation time has been assumed deterministic in sampling from a group of different mean operation times. Thus, because of the differences in stage operation times due to the variability of the operator's performance and/or unequal distribution of task times, the production line experiences various types of problems. In this paper we tried to see the effects of this imbalance of stage operation times in a just-in-time (JIT) production system. In addition to the implications of the simulation results, an indication for further research has been given in the conclusion.