I don't think for the cost it would be worth it to go up only 8cc. You would notice very little with such a small increase, unless compression were also increased. I installed a 146 tb kit on my yx140 because it was really cheap used and I was putting in a Z40 cam anyways. If you had quite a few miles on the bike and you needed to rebore the cylinder anyway, then maybe it would be worth your time if you could get it done cheap.is a 133cc light bore worth it? would you much improvement?