[trx]

will i took the head off the other day and i found like a small hole on the top of the piston on intake side on the right it looks like a 3 quater moon shape like a pin hole kind of ,,the motor is a 85 atc250r and this piston is huge compared to my old trx250r piston it looks way bigger with a flatter top and the skirt is thinner this is the first time i took the head off and looked to detail so i know its bored and its a different piston for sure and the the reed intake has a small port too it

this motor was built back in the 80's and my dad wasnt to sure what was done too it all he had the motor built by a guy

so what is this pin hole