New to dirt bikes

Do NOT buy that bike! Save the extra and get something of good quality like one of the Big 4 Japanese or Husky/Ktm.

If you're going to try motocross, buy yourself a
Honda CRF250R
Yamaha YZ250F
Kawasaki KX250F
Suzuki RMZ250.

If singletrack are more your thing, or you want something with a little bit more mellow power
Honda CRF250X
Yamaha WR250

If you're going to try trail riding in some main roads
Honda XR250R
Honda XR400R (don't be intimidated by the 400, it has less power than even the CRF250R)

Hare Scramble/GNCC
Honda CR125R
Yamaha YZ125
KTM XC 150 or 200
Kawasaki KX125 or KDX200/220.

You're first bike will probably not last you long as the more you get a hang of riding, the faster, and harder you will want to ride. I'm not a pro rider, but I can keep up the the guys who ride big 450's in the woods on my CRF250R. I ride the moto version in the woods for the weight saving purposes. Whatever you get POST PICS, AND SHARE YOUR FEELINGS. There are plenty of people on vital who will help you out getting it Dialed in. You need but to ask. I actually highly recommend getting the xr400 or xr250 to start out on as they are easier to ride than a 2 stroke like the 125's 200's and 220's, RUN FOREVER, and are EXTREMELY BULLETPROOF.

Most importantly, don't buy a used helmet, and always remember your protective gear. Don't skimp for the cheap stuff when it comes to your safety. HAVE FUN AND RIDE SAFE!

DO NOT BUY THAT BIKE

If you only riding trails, I'd say get your hands on like a DRZ 400 or XR 400. They're tanks and last forever. Keep in mind race bikes EDIT: (4 stroke race bikes) have high maintenance cost especially when top end needs redone. If you want to go fast but don't have a ton of money to spend, I'd recommend buying a used kx, cr, yz, rm 125 2 stroke or one of the trail bikes I listed above. I also agree with all the above post. But if you want to spend less money especially on long term maintenance used 2 stroke race bikes are the way to go.

Spend as much as you can afford on a good used name brand 250 4 stroke bike.
At 6' tall, any full size bike will work for you.
WR250's are a great all around bike.

I came across this thread and since there's a good recommendation here I would like to ask what bike can I replace Yamaha YZ125 with?

Take a look at YZ250 or Honda XR250R

Whats a better bike to buy 2011 rmz250 efi Or 2012 yz250f

Best all around bike or would a ktm250sx be better