What happened possibly????

[mighty1000]

Just want to get some ideas form others if you have ever seen a piston do this and why.
Thanks
Piston is out of a 98 arctic cat cougar 550 liquid cooled carbed, mag side.

 

[brian h]

running lean,to much air and not enough fuel

 

[Tippett]

LEAN, Air leak somewhere/Not enough fuel/carb boot cracking....... Go over everything.

 

[papajake]

did that 2 times with a yamaha phazer to much air not enough fuel

 

[Joholio]

Lean. Maybe a pice of trash in main jet or something if its jetted right for the elevation. Years ago I took my old 600RMK which was jetted for 4-5000' to Saskabush... Went like hell til I melted her down!

 

[CUSO]

It does look too lean, but why would it look like it was knocked out from the underside of the piston?

Is the underside of the crown purple?

 

[Warhawk]

Rule of thumb.

If it goes like it never gone before GET OFF THE GAS.
Or
If you ever say to yourself when riding " MAN THIS THING IS F#*KING WORKING AWSOME" get off the gas

 

[Shadam]

have you got a pic of the plug, dome ???

 

[daves]

Did u have the wright plugs in it ?

 

[moyiesledhead]

It does look too lean, but why would it look like it was knocked out from the underside of the piston?

Is the underside of the crown purple?

It was melted out from the top. Lean or wrong heat range plug.

 

[DRD]

Engine Basics: Detonation and Pre-Ignition by Allen W. Cline

 

[moyiesledhead]

Engine Basics: Detonation and Pre-Ignition by Allen W. Cline

Yup, pre-ignition will do it too. Used to suffer that a lot in the '70s with carbon buildup on those old pistons causing hot spots.....or like I said, spark plugs too hot of heat range. Be interesting to see what the plug & head look like.

 

[popcorn popper]

Yup poor fuel detonation and to hot of plug!

 

[moyiesledhead]

Yup poor fuel detonation and to hot of plug!

Nope, detonation won't do that. It'll pit the piston domes and break ring lands. Pre-ignition will put a hole in the middle.

 

[DRD]

"Detonation always precedes pre-ignition and the causes for this abnormal combustion are the same as those for detonation."

 

[moyiesledhead]

"Detonation always precedes pre-ignition and the causes for this abnormal combustion are the same as those for detonation."

Kinda flies right in the face of the first link you posted huh? How can detonation precede pre-ignition when it happens AFTER the spark? Even the experts can't agree!

 

[Sparky's]

Could be running to hot of plug as well. Melted down my dirt bike a few times to learn that

 

[popcorn popper]

Yes bottom line is bad fuel or wrong heat range plugs. Call it what you like!

 

[DRD]

Kinda flies right in the face of the first link you posted huh? How can detonation precede pre-ignition when it happens AFTER the spark? Even the experts can't agree!

Not really, if you think about it. The timing of the events during the "cycle" are different than the path it took to destroy the piston. If I had mild deto, not enough to stick a piston, but enough to oveheat something in the cylinder and cause pre-ignition what came first? The deto is after the spark starts the burn but could be the cause of pre-ignition by creating the condition or trigger (hot spot).

 

[moyiesledhead]

Not really, if you think about it. The timing of the events during the "cycle" are different than the path it took to destroy the piston. If I had mild deto, not enough to stick a piston, but enough to oveheat something in the cylinder and cause pre-ignition what came first? The deto is after the spark starts the burn but could be the cause of detonation by creating the condition (hot spot).

Hmmmmmm. Makes sense. Need to see the side of that piston to look for signs of det.