I own a couple of KTM 125's and find them to be very good motors. You found the jug to be out of round after going through 4 pistons. It should have been checked after the 1st piston was replaced. Problem may have been found and repaired. I have raced with my 125's with no unusual wear. If you have been a racer for 40 years, you know how racing bikes are.
I am interested in a KTM 125 SX and I have heard good and bad, so I am not sure what to do???
I own a 2002 KTM 125, and mine's been a great bike! It wasn't until last summer when it needed to be rebuilt. So I got 5 years on it, and I was wrapping it out.. but all in all, I'd recommend getting one.
I have had a 2002 KTM SX 125 since December 17 2009. I bought it used, and the owner before me only rode it twice, because he said the power was too much, and he prefers his 450f because the power is not as choppy.
So I bought it, and I love the bike, but the guy who I bought it from never took care of the poor thing; it had 3 year old gas in it and bad oil, and the chain and sprockets were bad, and the fork seals went out.
Now that I put the money into the bike, I LOVE it, it is an awesome bike, and the guys I go ridding with have a 2008 and a 2005 YZ 450f and CRF 250f, and I have no problem keeping up with them going across the ice. :)
The first problem was the jetting, but once I got the jetting right, it ran perfect, and in the back of the big book there's a jetting chart with a sea level and up :) Which was a huge help on my part.
I'm 13, and I saved up all my money for 2 years in a row, and bought it off of Craigslist. I personally think the bike is worth it.