Starting issues (Timing)

My bike is a 93 KX 125 it has a very recent bottom end rebuild on it. I bought the bike in pieces and took about a week to put it together, we did everything right and took our time. The first time we started it, it was easy like, 3 or 4 kicks. Then it was stolen by two worthless individuals, through the help of some friends I managed to get it back last friday. The problem is now it won't start unless the timing is advanced all the way and then it has no power. I'm wondering if dumb and dumber didn't fry my top end or something, I don't know that much about 2 strokes and this is my first bike. But I do know that it is firing on the down stroke because it backfires while you kick it. Any idea's on how to time it or what the problem may be is greatly appreciated. Thanks
Dennis

The timing should be re-adjusted to factory. And if it doesnt start, I would check the compression, then tear down the top end. Lookfor scoring, and cracks. Also check the power valve to make sure it is not damaged or stuck. If none of those work, I would say whoever stole your bike ran it for a long time at top end. Probably on a road. You say when it does start, it has no power. Like it wants to hit powerband, but there is something not letting it? If that is the case, you probably need new oil seals on the crank. Replacing them can be a pain in the ass if you split the case, and set it on the wrong side. Let me know what you find.
Jim