what happened to this piston

[gwcrim]

2001 PW80.  Lots of use.  Ran well and suddenly died.  This is the piston after I wiped it off with a rag.  Material was lost above the rings near the edge of the piston.  Cylinder had similar damage at the very top only.  There is oil in the tank.

[KX500freak]

this could point to detonation,
is the top of the piston battered and dented?
what fuel were you running ?

[gwcrim]

Top of the piston is OK.  Head looks good too.  Damage is just around the edge of the piston and the very top of the cylinder.  I run regular pump gas in it.  It's just a PW80 after all.

[demographic]

Top of the piston is OK.  Head looks good too.  Damage is just around the edge of the piston and the very top of the cylinder.  I run regular pump gas in it.  It's just a PW80 after all.

Aren't PWs two strokes?

Does it have autolube then?

[gwcrim]

Yes it has Autolube.  Could it be oil starvation?  Would that cause pinging?

[KXcam22]

Its difficult to tell fromt the pic.  I would suggest oil starvation from the autolube system.  On my sons PW80 I removed the autolube first thing and ran premix. Did you run the same fuel in another bike.  Long time ago a race team I was in all had a similar failure due to bad gas.  We all filled up at the same spot and blew up the same way and the same time.  It was strange seizure at the top side, if I recall. Cam.

[gwcrim]

I sure can bypass the oil injector.  We do have a few things around here that run premix.   

[KXcam22]

crim,
  It required a step leaner pilot and main but then ran excellent and no spooge.  Ran my 60:1 KX premix. Totally off topic but on mine I extended the tabs on the swingarm triangle where the shock bolts on.  Then you could run stock seat height or raise the seat height 3" which made it better for taller kids (and handle better). Had to add a chain roller to accomdate chain slack (used the chintzy KX one and got a nice one for the KX) and extend the kickstand, but a worthy mod that lasted though two kids. Cam.

[gwcrim]

This bike is on it's third kid.  Once it's up and running, I think it may go for sale.

[don46]

I think the key is in your first sentance "lots of use" it looks to have severe blow by, i would say not oil starvation, and if to much oil it could be knocking down the octane rating to far

[gwcrim]

Thats odd that you say that Don.  When I took the top end apart, it looked like there was too much oil in it.

[hughes]

I think the key is in your first sentance "lots of use" it looks to have severe blow by, i would say not oil starvation, and if to much oil it could be knocking down the octane rating to far

I agree. Looks like worn rings allowed the combustin gases to blow by. Also theres alot of carbon on the ring lands. She just look like a worn out piston/rings.

[gwcrim]

I got the parts back last week and part of the cylinder that slips in the cases was cracked off.  Probably could have used it but I shipped it back and they're going to sleeve it.  Hooie.

I also took the oil pump out and filled the hole with a rubber freeze plug.  We're going to run it in a few pee wee hare scrambles once it's back together.

In the meantime, I got the little guy a KX65, 2006 with rubber seams still between the knobs on the original tires.  He's figuring out the clutch slowly and he can't even tippy toe on it but he rides the snot out of it in 1st and 2nd.  Oh yeah... he's working on wheelies too.  I have lowering links on order.