Crack in piston???

[LONG-ROD]

I have a pro-x 310 kit and I tore it down to find 3 cracks one in the very bottom of the skirt on the intake side, running vertical. There are still etching marks on the sleeve, so it appears to be a pretty fresh rebuild. What would cause this. Ran rich top of piston is black, and dome is chewed up, and ran pump gas.

Mods includ the 310 kit boyesen radvalve, carbon reeds, (pro series) and pro circuit pipe, and some sort of hot rods crank.



also can some direct me to where I can get a cool head for this kit. and where the best place to send it to have it re sleeved and a piston matched to it.

[GPracer2500]

Loose piston-to-cylinder clearance can do that (because the were set up loose to start with or because the bore and/or piston is worn). Also, a cast piston that just has too many hours on it can develop cracks in the skirt. No matter the precise cause, a forged piston will resist cracking more than a cast piston.

[LONG-ROD]

Thanks I was wondering about that, it looks like this piston was hitting on three points in the cylinder, and it looks like it never hit anywhere else, I also have holes in both reeds, When I put a new sleeve and piston in, standard 310 will I need to do some rejetting, I think I need to go smaller with the main and piolet jet was kinda rich before in the summer and got better in the winter whern temps droped, any help would be great, tyhanks guys.