I have been checking out several threads on here regarding dirt bikes and sizes but I can not find the information I am looking for in my situation. My son needs an upgrade. I was thinking of converting his 150R to the big wheel which takes some time and money but then it is still going to be smaller than the normal bike. Maybe it would be better to get a different bike altogether, a larger one. The problem is he weighs 125lbs now and he is only 5' 1". I feel the 150R is under powered for his weight but he is too short for anything else. I see some of you have lowered bikes so they fit the rider but I worry a 250 might be too much power for him. I have had him on every bike known as he has grown up, since he was 7 and now he is 14 so he has experience on two wheels, however, he is not a dare devil throttle jockey by any means. I am sure if he has more power and bigger wheels he will be a much happier rider, especially in those sand washes. I tend to shy away from 2 strokes because we like the smooth power of the 4's but that may be negotiated. What are your thoughts?