cr125 piston

[ryanrambo24]

I ride a cr125 91' and i remember the first time i rebuilt my engine the previous owner had 3 holes drilled in the piston, just under the rings on the exhaust side exact middlelike where the post is on the exhaust port. I was wondering if you or anyone had ever done this or heard of it , what is this done? any other good tips for a successful top end rebuild

 

[Robin13]

Those are there to lubricate and cool the exhaust bridge. The bridge expands faster when the engine heats up than the rest of the cilinder because of its relatively small size and large surface area. So to cool it and lubricate it, the piston is drilled. My wiseco came pre drilled, and with instructions in case it wasn't.
Wash your bike weel before rebuilding your topend so no dirt will fall into the cases/cilinder.