Two Stroke Motocross

Two Stroke Motocross Forum => Technical => Topic started by: dirtbikersa on July 14, 2012, 11:56:58 AM

Title: Piston Failure
Post by: dirtbikersa on July 14, 2012, 11:56:58 AM

Good day all, was out riding the weekend when I ran into some troubles. I suspected something was wrong when the bike was not starting so I just left it. Anyway I got around to tearing it down today and was surprised at what I saw when I removed the piston. See pics -










The piston has just under 50hrs on it . Any ideas as to what could have caused this? The cylinder is still in perfect condition and no signs of damage. I would think the broken piece from the piston has blown out the exhaust port and would not of gone down into crankcase.

Title: Piston Failure
Post by: 2T Institute on July 14, 2012, 02:20:59 PM

Blow by.
Detonation.

Title: Piston Failure
Post by: dirtbikersa on July 14, 2012, 02:40:00 PM

What are guys thoughts on metal particles getting into bottom end. Seems almost impossible to me, if it was on bottom of piston it would of got sucked in but being on top of the piston it would surely get blown out exhaust port.

Title: Piston Failure
Post by: SachsGS on July 14, 2012, 03:43:38 PM

Fair bit of rattling going on there.The aluminum is harmless but it also looks like your steel ring locating pin disappeared,probably out the exhaust port.

Title: Piston Failure
Post by: metal_miracle on July 14, 2012, 03:46:26 PM

not sure if its just the light..

but it looks looks like it hit the head too..

have you checked the play on the con rod ?

Title: Piston Failure
Post by: dirtbikersa on July 14, 2012, 10:47:28 PM

no up or down movement on con rod just side to side...

Title: Piston Failure
Post by: scotty dog on July 14, 2012, 11:11:35 PM

looks like detonation to me too, must have been pinging its head off