How to Do a Top End on a Honda CR250by Bryan Clark; Updated October 25, 2017
Items you will need
2 new C-clips
New wrist pin
Needle nose pliers
Based on your use of your CR250, you should rebuild the top end after every 40 to 100 hours of use. You will notice a loss in power or a weak idle when your top end needs to be rebuilt. It is a basic job that can be done at home. When replacing your piston, you should always replace your C-clips and wrist pins. Ensure that you purchase your replacement piston from a reputable manufacturer.
Remove the gas tank by removing the bolts that secure it.
Remove the rear portion of the frame by removing the bolts that secure it.
Drain the coolant from your motorcycle by removing the drain plug at the bottom of the engine.
Use a tusk spring puller to remove the springs that secure the exhaust pipe. Remove the pipe.
Remove the top motor mount head stay by removing the bolts that secure it.
Remove the spark plug by unscrewing it.
Remove the radiator hoses by unscrewing the clamps that secure them.
Remove the engine head by removing the six bolts that secure it.
Remove the head gasket by pulling it out of its socket.
Pull out the two centering dowels.
Remove the power valve cover by removing the bolts that secure it.
Remove the linkage bolt using a socket wrench.
Loosen the cylinder bolts and remove the cylinder.
Pull the C-clip out of the groove in the cylinder using a small flat head screwdriver.
Slide out the wrist pin. The piston is now disconnected from the connecting rod. Remove the old piston
Slide the new piston onto the connecting rod.
Install the new C-clip by pressing it into the groove on the cylinder.
Slide the new wrist pin into its slot.
Slide on the second C-clip using needle nose pliers.
Slide the cylinder back onto the bike and tighten it back into place. Tighten the bolts in a crisscross pattern for even tightening.
Reassemble the rest of your bike in the exact opposite order that you disassembled it.