2003 KX 250 Engine...

[Flynbyu]

Hello,

I'm posting for a friend who has engine problems on his KX 250. He has removed the top end, and as suspected, he has a broken piston around the skirt. The top portion of the cylinder walls look good. There is no visible damage.
My concern is the rod and bearings. There seems to be a little play with the rod, meaning you can physically move it from left to right a few centimeters when the rod is in the full up position. The range of movement is good with the rod and crank. You can complete a complete revolution in either direction without any resistance or any grinding. Is the play with the rod normal?

My recommendation to him was to crack the case and check for any damage to the crank. He's on a tight budget, so any pointers that I can forward to him, or another site you may know of that I can reference, it would be appreciated. Thanks-

 

[Rcannon]

I have brokes pistons on several different bikes. I was able to flush the chunks out of the lower end using kerosene and compressed air. Probalby not the most safe way, but cheaper than splitting the cases.

 

[adam728]

Side to side play in the rod is normal, although I hope you meant a few millimeters (if that) instead of centimeters. What is important is the up and down play. There should be none.

As Rcannon stated, it is usually possible to flush out the lower end, although full tear down is best. I use mineral spirits followed by a little carb cleaner, then put some 2 stoke oil on the bearings and spin everything around good a few times.

 

[Flynbyu]

I'll pass the info to my homie....Thanks for the input. The play is very minor, up down motion is good, with no play.

 

[rickyd]

I would find out why the skirt broke.. An old bike of mine broke a skirt, found out the bore was tapered, meaning the piston had a small wobble.. Causing the skirt too get hung up on the exhaust port..
Rick