The maintenance schedule will not be anywhere near as intense for a 2-stroke when compared to a 4. The top end will probably be the biggest hit on your wallet. Expect to do this every year or two (a lot more if you get into racing with it). People on here will say stuff to the effect like, you have to waste time measuring the oil to mix in with the gas. If you think about it, as much as you're changing the oil on your racing 4 stroke like maintenance requires, you'll be dumping every 2-3 rides almost the equivalent of what I'm mixing in. Use a good synthetic oil for whatever bike you choose (my personal favorite is klotz, but there's a lot of good stuff out there). Of the 3 bikes you listed the YZ is the best bet. Honda's CR250 is no longer in production and had weird jetting issues. The KTM SX is super light but does not have the power spread of the Yamaha or it's spot-on suspension. Is the new bike going to be used for trail or MX track? The KTM 250 XC would be a better bet if you plan on riding woods.

That really isn't the best way to find a dirt bike for sale that you are looking for. The likelyhood that somone would respond with one within your price range and within driving distance and the type you are looking is slim to none.

Your best bet would just be to go on ebay or craigslist. If there aren't any up, you could try looking under ebays completed listings at bikes that didn't sell and ask to see if they still have it and it's still for sale.

And one last thing, 2 stroke vs 4 stroke really does make a difference. the 2 stroke 250 would be more along the lines of a 4 stroke 450 powerwise. I'd reccomend a yz250f.

Ok, most def a 125 is too small for you, 250cc is about what you need, If your looking for speed get a 2 stroke engine with a power band and a jetted carb. If your just looking for something to ride casually and you don't want to show-off on it, get a stock 4 stroke.

Two-stroke engines have the potential for about twice the power in the same size because there are twice as many power strokes per revolution.

I'f your just starting out riding dirtbikes and don't know how very well DO NOT GET A 2 STROKE.
Start out with a 4 stroke or you might kill yourself, fast dirbikes are very dangerous, I know from experience.

other than that a 125 is too small for you, I have a 250 and I'm 5'8'' 155lbs.

As I said in your other question to have a look at the 4 stroke 250cc but you are a good size and height for both the yz125cc and the cr125cc but you would also be fine on a crf250r or a kx250f

I think your friends have it about right. I like 2 strokes but in 2009 every one is going to stop making them and go to 4 strokes. if you wanted a 2 stroke I would go with a 125cc two stroke. if you want a 4 stroke, i would say no smaller then 250cc.

I think you should look for something in the 250cc range, good power, balanced. And you can touch the ground….j/k Try the 250, RM250 from Suzuki is nice

Agree with him, buy a larger one, and maby he will pay for a little of it after he rides it a 125cc-250cc is good nothing more

You are going to grow a little more before you wear out a bike. A 125 might be too small for you. I would look into a 250cc four stroke machine. Or I would look at the new KTM SX144 two stroke

Pressure from world bodies over noise pollution has stopped production on a couple of the well known brands of 125cc including Kawasaki and Honda. Popularity to race the 125cc has also been down as they quite often have to race against the 4 stroke 250cc and they usually get beaten (of course there is exception to that depending upon the rider onboard).
Part of the reason that honda developed the 150cc was to replace the 2 stroke 85cc although I don't know if it has been as successful as they would have hoped as the idea was for them to race against the 85cc and in America they don't allow that as they race in their own class. Australia has them racing against the 85cc.

A 125cc two-stroke or a 250cc four-stroke would be a good choice for your age and weight. Choosing between a two and four stroke is mostly based on personal preference. Each has their own advantage and disadvantage over the other. The most obvious difference is that two-strokes require you mix your oil with your gas. However Two-strokes are also lighter than four-strokes and have a much simpler design. It usually costs less to modify and repair a two-stroke engine than a four-stroke engine. But two-strokes can also be finicky and a lot less forgiving than a four-stroke if you don't know how to tune it properly. four-strokes also have a more user friendly powerband, they tend to make more power than two-strokes on lower RPM's so it's much easier to putt around and go as opposed to a two-stroke which tends to like being revved high. I personally prefer a two-stroke over a four. But you need to decide which would suit your needs better.

Choosing a brand of bike is the same also, whether it's Yamaha, Honda, Suzuki, Kawasaki or KTM. All manufacturers have their advantages and disadvantages over the other. Just keep in mind there's nothing that will affect performance, handling and reliability more than how you set your bike up, and how good of a rider you are. I've had friends on modified 250's and 450's get spanked by 8 year olds on 80's for that same reason.

So do some research and see which bike would suit your needs better. Once you buy your bike be sure to also get a repair manual for it and learn how everything works and how to properly set it up. You'll end up being safer, faster, and a better rider.

Good luck with your purchase.