Anyone ever heard of a motor doing this?

[Jpoutlaw250R]

Uh this weekend when i was racin my motor just siezed on me so I thought that just the piston had weled to the cylinder or somethin like that but when i got it apart the whole piston skirt shattered. Like a quarter of an inch or so below the bottom ring and down the whole thing was busted off and in lots of pieces in the crank area. It tore up the cylinder pretty good too, and pitted out the head quite a bit too. The top of the piston was all pitted up around the outside and stuff but it was still black not like it went lean or somethin. I am thinkin it mighto f been detonation or somethin like that that caused it. :huh Well just wonderin if anyone else has had this happened or heard of it. I will try to get pictures later but not sure how to yet. Thanks Later Pete Oh yea forgot to put but this is on my 250R.

[skemp]

It may have been detonation, but usually the detonation starts around the outside of the piston and travels down into the ring land, rather than the skirt. It is difficult to tell without seeing it. A ring may have also caught a port, or spun. That would be my guess without seeing it physically.

[AndrewRRR]

if the side of the piston has black it sounds like you caught a ring on a port and broke it. From there more carnage ensues. I hope you have some money saved up, lol.

[jonc623]

if the piston was black it most likely was not lean i would look somewhere else i have had pistons just break like you have said

[boogiechile]

detenation means that the fuel ignites early before the plug fires and the when the plug fire it ignites again. This can cuase a severe rocking motion or side load on the piston since the detenation usualy is ignited on the side of the chanber or piston. This rocking puts a larger load against the piston skirt and can break it. One thing leads to another and its not good. were you running a lot of compression? on pump gas?

[Pele05]

My freinds ride two stokes and we have rebuilt them a couple of times. Its not uncommon for the piston skirt to break. How were the rings looking after you took it apart. On the motors I've seen the rings wore out and the piston got so hot something has to give. Time to bore and rebuild.

[Pele05]

My freinds ride two stokes and we have rebuilt them a couple of times. Its not uncommon for the piston skirt to break. How were the rings looking after you took it apart. On the motors I've seen the rings wore out and the piston got so hot something has to give. Time to bore and rebuild.

[airheadedduner]

Sounds like it just had to much clearence to me. My brothers lt did that not to long ago. Ran great, shut it off and it wouldn't start back up.

What oil do you run? Castor based oils will varish the sides of the piston over time.

[velocityatv]

Did you have a lot of piston slap goin on before this happend? how long has it been sence the last bore? 2 strokes are funny, they can run great even with the piston slappin around in there. If you ignore the noise the piston will slap itself around enough that the weakest link cracks witch would be the skirt and walla it time to tear it down. Don't think that 2 strokes can run for 5-10 years without rebuilding a top end. I rebuild 1-2 times a season and I just think of it as insurance.

[AndrewRRR]

2 strokes CAN run for 5-10 years without a rebuild but you aren't going to have any compression afterwards, lol. My buddy has an old yamaha 100 that hasn't been rebuilt in at least that long but you can bet compression isn't there.
It's important to rebuild every couple years at least.
The same friend recently rebuilt a banshee that wasn't running right. Turned out both rings on one cylinder were completely gone. It had about 50psi one cyl and 90 on the other. Talk about blowby! That'll varnish the exhaust side of the piston like no other, plus allow the piston to rock enough to possibly snag the skirt on the port edge and things get very expensive very quickly.

[Jpoutlaw250R]

Hey thanks, Yea I couldn't really tell any slappin sounds but not sure cause this is my first 2 stroke i have had. When i first got it about 6 months ago or so it was just freshly rebuilt with only like and hour on it and then i was runnin castor 927 with the supreme pump gas in it. After a while i was noticin the plug comin loose and i heard that might of been cause of detonation so i started runnin race gas then with amsoil and that solved the plug problem and it ran awesome like that. So i am wonderin if when i was runnin the pump gas if it was detonation then that wore on the piston :confused: Now I am thinkin that ill end up w/a new crank and rod, cause the rod is bent and crank is scarred up a lil, and thinkin about maybe gettin the ct racin 310 bolt on kit. Was also wonderin if anyone on here had any experience with that? Thanks again for all the help. Later Pete