New Game: how'd I roach that piston?

[bradzdotcom]

put me down as leaning toward the "too lean" explanation.

like roger, i've done lots of lean pistons, most of which were executed by my right wrist.
it just doesn't look like anything else i've seen during an engine autopsy.
put me down for the "ethopian effect" (not enough of the right stuff to eat).

[roger albert]

> most of which were executed by my right wrist

Isn't that the truth. When doing this for actual sport, it's easy to sabotage yourself.
It's another reason I tend very heavily towards 4-strokes. I.e. in that regards, I'm with markjenn in finding it a lot easier to destroy a 2stroke. I ran one of my 4s stupid lean on top end earlier this year. If it had been warmer, or the course a bit longer or less technical, then my new motor (which cost about what the entire bike did new) would likely have looked a bit like the pix here. As it was, it came out fine, just down on power up top a bit. If I'd screwed up that badly on a decently set up 2stroke...Yuck. (I was also helped by inadvertently being too rich on bottom - drastically, which of course cooled the piston a great deal when off the throttle -- something performance dirtbikes, especially 2-Strokes, do on purpose.

[1100s nut]

Yep, lean is mean to an engine of any sort. In fact my 850i goes into automatic fuel enrichment at speeds above...IIRC 150 or 160 mph to keep cyc. temps down. I get about 14 mpg I guess at 160 prolly goes to 6-8 mpg. Computor will not allow speeds above 155 in the states though... I don`t drive fast anyway.

Lane

[bradzdotcom]

roger~
in the 2-stroke days, i think my record was about 2.5~3 minutes of life out of a husky i was warming up by running up and down a sandwash.
it warmed up all right....and kept right on going.

wish i had a buck for everytime i've heard that funny exhaust noise that occurs nano-seconds before it squeaks to a standstill.

[bigscience]

based only on the pics you've seen here Chris at San Jose guessed a bad injector causing it to lean out. Bill has a good point that it might be the wiring to the injector if it's not the injector itself which I will have to check. it has also been suggested that a fault might be found in the chip since I've got an FIM chip in it. But I tend not to think the chip is at fault since it was not installed when the first piston meltdown occurred. I'm not even sure if the chip controls the injectors individually or not- anyone know that?

[Flatbutt1]

Since a weal injector can cause so much damage, is there anything we can do to see this coming? Any telltales longer than 5 nanoseconds prior to failure?

[bigscience]

not really sure flatty, I did notice a drop in milage for some weeks before total failure, probably due to the piston being upset in the cylinder and abrading the walls. with the rings not seating properly I'm sure there was some blow-by, which I'm guessing is what caused my oil sight glass to start weeping. this was occurring probably weeks if not months before it went completely. Not sure these symptoms (only evident in retrospect) would do much good though, since by the time you start seeing this kind of stuff it's already too late to save yourself much. other than the long walk home that is.

[JimMoore]

I gotta believe you would notice some performance issues if you ere lean enough to do that kind of damage. No knocking / detonation? No missing at the top end?