Your only 125lbsOne word, "momentum".
If you can keep your momentum up in corners (via proper technique), the size of the engine isn't that important. One reason 450f's are popular, especially with beginners as that they'll take a corner pretty slow and then use the 450's power to get over the jump. Instead of railing the corner to keep your speed (momentum) up, so that you can clear the next jump.
However due to your weight you're an exception, I would probably get a 450f.
My 125lbs body can't handle a 450f, so don't plan on seeing me on one anytime soon.
I agree, the yamaha doesn't still work on 2 stroke engineering but they devolped a great bike in 2006 and still produces it. You will love the SSS stock suspension still stock equipt on the YZ series, it is to die for.Dont worry about all of that feathering the clutch stuff until you are confident on your bike, just learn to ride it first If you are dong track and trail for 2t id say YZ250 for 4t you have to use an MX bike, but its your choice
BTW welcome to the forum
You probably could use a 450 bike as long as you don't get overly excited and try to do more than you can handle Thats the main thing to remember. When I have my 250 fo stroke under a heavy load it has to chug a little, but it was closer to 300 at the time. (I don't weigh 300 btw ) Personally I would reccomend a 450 4 stroke just because thats what I do good on and I love the power devilery. As far as you go I couldn't help Everyone has their own prefrences so if you can take a test ride on a friends bike then all the betterLmao, you guys are my kind of people. Ahaha I know that wasn't a fat joke James. I'm just messing with you. Lol I like saying that to people. Ahaha I'm not fat, but I'm not solid muscle either. I'm just big. Well I certainly don't want to be lazy on a dirt bike. Haha I want to develope technique and skill. The reason I was thinking a 450 is because I'm sure at some point I'd get onto an MX track. And I want a bike with enough power to get me over all the jumps no matter the distabce, seeing as I'm bigger and all. So I don't think a 250f will have enough power for that. Or a 250 smoker. Do they? I know technique will be involved no matter which 250 I choose. Like feathering the clutch, and shifting properly and all that. But I've heard people saying you have to ride a 250f harder to keep the revshigher so you can maintain speed..........