engine seizing

[adamscrf]

have a 125 and just rebuilt the bottom and top end recently and today the engine cold seized about 30 seconds after start up, or so i thought... I tore the engine down tonight expecting to see a bad piston and cylinder but everything looked like new, no marks on piston or cylinder, crank in spec, and crank bearings are tight.

when the bike first starts it feels fine then within 30 seconds the bike starts makings a draging/grinding noise and the motor starts laboring very hard as if its under a load. does anyone have a clue as to what this might be?????

[PoorBoyRacing162]

had a cr 125 that did this once and the piston was too big, it was a wiseco piston and it was expanding too fast and seizing into the cylinder. Just a thought maybe try a different piston. Good luck

[nopremix]

I would agree with the expanding piston issue.... Usually the forged Wiseco pistons are louder until they warm up / expand and fit the cylinder, but in your case its too tight from the start.