A couple things here: First of all I bought a 125 from the Rogers and it was a 125, bone stock bike. It had an OEM exhaust and my son crashed and put a hole in it so, I chose to put a FMF exhaust on it because it was cheaper than factory. But it wasn't a performance thing it was a financial thing. Then we had a couple issues with the engine so, I took a cylinder and sent it out to an engine builder because I thought that might take care of some of the issues we were having and had it bored to a 139. Well that lasted about 3 weeks and then she blew. My son also told me he really couldn't tell a difference in the 139 over the 125. So, we decided to go with an original OEM 125 cylinder, head and piston and it has been fine ever since. So, for those of you that want to do mod's, I would recommend sticking with what the Yamaha engineers designed.
To the guy that said, "OMA is a joke", could you elaborate on that topic a bit, I don't understand why you feel that way.
I know a lot of people only care about keeping classes as fair as humanly possible, meaning lets make a 125cc class with a maximum weight of 275 pounds combined rider bike weight, with a maximum of 12 psi in the tires, and your reed cage cannot have reeds with more than 60% of its orginal ridigity. Yes its a word, dont bother looking it up.
While, I understand your point and that you are making light of this conversation, there is truth in the weight to horsepower ratio. Yes my son is a bit on the heavy side but he is not obese and ever since we have been in this sport he has had to race against kids that are normal weight or in some case's twigs. For example, he is some where between 175/180 lbs, definitely over weight but how is it fair that he has to race the same horsepower motor as the kid next to him that weights 115lbs, honestly, its not fair. He is at a serious disadvantage. When he was on mini's, the bike and more specifically the suspension just wasn't made for his weight so, as usual we got pushed up to a bigger bike but he is still racing against kids and young men that weigh considerably less than him. I'm not complaining, I am just pointing out an obvious fact that most people probably never consider because one thing I have learned in life is if it doesn't affect someone directly then who gives a rats butt. So, when I hear that someone's bikes are mod'ed, I do believe it is a form of cheating but I still believe the rider is a much bigger factor than the bore. So, if we want a level playing field then lets add weight to everyones bikes until all the riders are riding the exact same weighted bike and rider combination, that is truly fair, but I gaurantee no one will be willing to step up to the plate and add an extra 30, 40 or 50 lbs to there kids bike, why not because that would be unfair to their kid. Btw don't talk to me about my son losing weight that is not the point of my post and he is working on it as we speak. I am just trying to say that while there are rules for the bore because of an unfair horsepower advantage isn't it also an unfair horsepower advantage when one rider is 50 lbs heavier than the kid lined up next to him. I'll answer that question.... Hells Ya!!!!! So let take this back to where it should be and that is, the better rider will usually win regardless of the cheating the rider is doing. BTW my son raced his 250f in the 450f class and even with the weight and horse power disadvantage he did better in that class than the others he competed in, which were 250 classes. So, while I know we have to have rules and they should be followed it isn't always as cut and dry as it seems to be, there are other circumstances that give some kids advantages over others. A quick one that comes to mind is how about the kid that has the latest, greatest bikes vs the kid that is on an older, ragged out bike and that is his only one, is that truly fair, probably not. How about the kid that gets to ride all the time or goes to training facilities vs the kid that can't afford it, again not a bore issue but definitely an unfair advantage. I could go on and on but there is way more to this racing thing than what the cheaters are doing at the end of the day it should be about fun, learning how to compete no matter what your up against and the friendships we are all making.