Blown Motor?

[97Kawi250]

So I installed my new exhaust system; fatty on the front and turbine core II on the rear.  (long story short, I ordered the gnarly for low end torq but the shop gave me the wrong one. Didnt realize till I installed it so I said screw it....)  First day at the track it was running well. Tons more power both low and top end. Running great, I loved the new mod! Then after about 2-3 hours of riding something went seriously wrong. I was in mid 5th gear on the long oval fast track when all the sudden the sound of the bike cracked and went into a low pitched rattle or banging sound. (kind of like the sound of the bike with out the tail pipe, but much lower pitched) It was an applified version of a playing card in the spokes of a bicycle, if you will. The bike would run/idle but only if I kept giving it gas. I immediatly pulled of and pushed it to the truck. I thought the engine had blown but there was no smoke or oil leaking. It is almost as if the new exhaust increased the performance so much that the motor could not handle it.

Does anyone have any ideas as to what could have happened. Is it something major? I am being optimistic when I hope that it's an easier and less expensive fix because the engine still runs.

Thanks in advance for the help. And by the way, great site! I was excited to find a community of KX riders on line

[kxs in oz]

 Hi pull off your pipe look at piston see if it has any chips cracks etc if it all looks good then sounds like you may have done big end bearing or maybe a main bearing best of luck

[eprovenzano]

 

  Hi pull off your pipe look at piston see if it has any chips cracks etc if it all looks good then sounds like you may have done big end bearing or maybe a main bearing best of luck 
 

 Good advise.  1st check the piston for signs of wear or distress. Have you ever done a leak down Compression test?  If you have the data from previous test, at least you would know how much the compression changed.   

 Keep us informed as to what you find.

 Welcome to the forum.

[KXcam22]

97Kawi,
  doesn't sound good. If you turn the motor slowly by hand over with the kickstart and listen/feel you might be able to tell something.  Also pull the plug and the pipe and have a look with a flashlight.  Any big rod ends I have blown, the motor died right away.  Post back with what you find.  Hope this helps. Cam.

[FPMXer]

From the sound of things you roasted the bottom end. My sons kx60 did the same thing to him and had the same symptoms. When you pull the jug off and look at the bottom end the big end of the rod will or should have a nice shade of blue.

[kx666]

 
before you get too deep, check your pipe. the FMF pip is much thinner than stock.

if you hit a rock or somthing they crack really easy. the k5 has much more vibration and pressure, allowing this to be fairly common.

...at least we hope

[Mudshark]

It's been a while, any news on what happened yet???