Looking at buying a Yamaha TT-R125 to learn the basics on and do some trail riding. Found one for $500 that needs a new carb, but according to the seller, that's all that's wrong. I don't intend on keeping my first bike very long, one I save some money and get comfortable, I'll be buying a dual sport 250. Here are the questions I have: Are all ttr125's 4-stroke? Is there a way to raise the tension in the rear arm to not drop too far? And is installing a new carb pretty easy for someone who is technically inclined? Thanks for reading my newbie questions!