I was surprised how thin the front down tube is. This portion of the frame is monocoque sheet metal.

 

My tank dosen't have all those bumps and wavy whatnots in it. Maybe yours got ran over by a truck out behind the dealership ?

 

If I saw an X-Ray like that, I'd be thinking trauma - not stress fracture.

 

That radiator has a hole in it too.

 

I'm actually not surprised by this. In my early research related to the KLX, I read of that happening to the KLX300R ... it seems there were multiple reports, though rare. I never found any pictures of breakage - at least any that I had access to. The most complete story I remember is someone letting a kid borrow his bike; the kid then proceeded to lose control and crash into a neighbor's porch, snapping the bike in half in the process, if I recall correctly. I think others were on bikes that were ridden hard...like MX style. I think some of these discussions were on Thumpertalk (a site which I am not a member).

The most convincing evidence I found was actually this: Stroker KLX.
I had read of people reinforcing this part of the KLX300 frame, but these are the only pictures that actually show anyone doing it. Obviously, this is not something a person does on a whim.

With proof that people actually did reinforce the KLX300 frame, along with proof that it is possible to break the KLX250S frame...well, it is what it is. At a minimum, I'd say if you are jumping your KLX, you need to watch out. Maybe think about reinforcing the frame.

I know that when I crashed hard in the fall of '11, my bike went end over end. After that, I spent a lot of time looking over that specific part of my frame for damage, based on what I'd read. Fortunately for me, my bike wasn't damaged.

Off on a tangent, another well known 'weak' area of this style Kawasaki frame (at least some of earlier perimeter designs) was in the cradle area, near the swingarm. Cracking was not uncommon. A recommended modification for hard ridden bikes was to add some gussets. Eric Gorr's book (at least the second edition) discusses this. Others do too, I'm sure.
edit: Now that I look closer, that Stroker KLX has those spots reinforced too.

I suppose if someone could talk to Larry Roessler, he might have some insight.

 

Nice research Lutz!

 

idk what he was doing wrong besides maybe a bad frame from the factory cus ive motoed the hell out of my bike and blasted desert whoops for hours and this is yet to happen to my bike. he said he had 26k km with is about 16K miles, my bike has 23k for referance. one thing i want to point out about the stroker reinforcments is that is on the flat sides of the frame above the radiator mounts if i can see that right. so in that case it wouldnt have helped in this instance (as the breaks are below that point), but the other bike i saw this kind of thing happen to it tore the steering stem out of the frame iirc, and in that case it would have helped then. i think some kid had wheeled the bike into a porch on that one, it was on here a year or so ago. also the tube broke pretty clean, especially the top tubes. i would think a wreck would have twisted it more then that and if he was jumping i would think it would tear the steam out the frame instead of breaking all three tubes (hence why stroker has the reinforcments where they are). probably a bad frame if i had to call it. nice find though and thanks for shairing.

 

looks like that thing got dropped off a mountain. Serious impact had to occur.

 

I'd be in touch with Kawasaki so fast it would make your head spin. If for no other reason than that they should want to see it and figure what happened.

My guesstimate would be that a stress riser started at the weld and a crack worked its way back far enough for the metal to quite literally tear from there.

Personal opinion, Kawasaki should warranty the frame as a good will warranty since, as said, it should NOT fail like that and they should take a good look at what and why.

Please let us know what happens.