Piston skirt came apart (pics)

03rmking · May 18, 2010

Pics are from an 08 M8 boondocker PG turbo. Maybe 8-10 rides on new pistons. Replaced them for no other reason than to be safe after almost 2000 turbo miles. Never had an issue before this. Was running 6.9lbs boost at 8230rpm, boondocker box says the injectors were at 84. Elevation was around 6-7k.

Two rides earlier same side had a plug come loose. Two rides later same side comes apart.

Running pump premium as always.

Any idea what could cause this?

03rmking · May 18, 2010

Here's a pic of the other piston. All plugs were nice brown and oily.

Rms Rydning · May 18, 2010

Looks like you have detonated the **** out of that pistons. Lucky you it was a AC engine so the rest is still ok.

How many times have you got the engine lamp up while riding?

03rmking · May 18, 2010

Rydning said:
Looks like you have detonated the **** out of that pistons. Lucky you it was a AC engine so the rest is still ok.

How many times have you got the engine lamp up while riding?

Never.

What I don't understand is why I was able to put 2k miles on at boost levels between 7-10lbs on the same fuel at same elevation and have no deto. Then run a safe 6.9lbs and kaboom.

Keep in mind alot of those marks on the piston are from smashing piston debris around.

backcountryislife · May 18, 2010

03rmking said:
Keep in mind alot of those marks on the piston are from smashing piston debris around.

At first I was thinking the same thing (that it was det), but unless you had your bd box trimmed way to one side, it looks like that's just impact.

Could it be something as simple as just having been dropped or something? A weak skirt from the get go?

TIM · May 18, 2010

I am suprised that you could run just straight premium pump gas.

03rmking · May 18, 2010

backcountryislife said:
At first I was thinking the same thing (that it was det), but unless you had your bd box trimmed way to one side, it looks like that's just impact.

Could it be something as simple as just having been dropped or something? A weak skirt from the get go?

Possible I suppose. I didn't put the new pistons in myself, so hard to say. I hate to rebuild it without pin pointing a specific cause.

It's the plug coming loose a week prior that makes me wonder if it was deto. Or is that merely a coincidence.

TIM said:
I am suprised that you could run just straight premium pump gas.

There's about 3 sleds around with this EXACT setup that probably have 10k-15k miles on them combined with no issues until this.

If it is a lean issue, what would lean out one side only. Crank seal?

When I pulled it apart the heat shield under the Y-pipe was spattered with oil residue on the same side. No real bad, but definitely a coating on the shield and underneath side of the charge tube. Thought originally it was coming from the exhaust donut, but now have my doubts. Perhaps something not sealing right?

Boyko · May 18, 2010

A sparkplug backing out is a sign of deto, if it was just loose you would not get to to far before it popped out. Any chance it ate somthing to cause the skirt to brake, it was not lean........ this is a tricky one

diggerdown · May 18, 2010

It doesn't look like deto to me, I would wonder about a wrist pin that was too tight and caused the skirt to slap the walls. I've also wondered if a guy had one plug fail, could the uneven ignition pressure creat enough force at high rpm to slap a skirt?

SNOW JW · May 18, 2010

Plugs going loose is a tell-tell sign of Deto. Mix some AV gas in there or race torco anything. Looks like you may have got some crappy fuel happens allot. $5 extra bucks of Av in the tank goes a longs ways and also lets you turn up the boost a touch as well.

hatchers · May 18, 2010

plugs on my M have got loose several times...ive also removed the M8 pep boys knock sensor for most of its life, the m1000 does not have one beacuse cat cant get this $2 knock sensor to work on the M1000......so whos to say it means much on the M8?

also, i would only hit the knock sensor above 15ish lbs, ran at 16-20 for over 200 miles, straight 112

last 300 miles on pump at 8lbs and the knock sensor is back on the head, all good

to answer why this may have happened to you - im guessing you live in the 509:face-icon-small-win, and im guessing the 509 only has E10 pump?....if so, you are basically pooring alcohol in your engine, and alcohol loves to chase away the oil these 2 stokes need to not burn down:face-icon-small-coo

i just noticed E-10 is slowly taking over Utah, guess its back to the 55 gallon barrals:face-icon-small-dis

03rmking · May 18, 2010

hatchers said:
plugs on my M have got loose several times...ive also removed the M8 pep boys knock sensor for most of its life, the m1000 does not have one beacuse cat cant get this $2 knock sensor to work on the M1000......so whos to say it means much on the M8?

also, i would only hit the knock sensor above 15ish lbs, ran at 16-20 for over 200 miles, straight 112

last 300 miles on pump at 8lbs and the knock sensor is back on the head, all good

to answer why this may have happened to you - im guessing you live in the 509:face-icon-small-win, and im guessing the 509 only has E10 pump?....if so, you are basically pooring alcohol in your engine, and alcohol loves to chase away the oil these 2 stokes need to not burn down:face-icon-small-coo

i just noticed E-10 is slowly taking over Utah, guess its back to the 55 gallon barrals:face-icon-small-dis

Yes our fuel has ethanol. But it also did last season. No change in the fuel it's been burning for 2000 miles. I was in Revy when it happened. Started the day burning Idaho fuel, dumped my 5 gal of Canadian 94 octane and this happened few hours later.

hatchers · May 18, 2010

oh shiz, i did not enlarge the pics and look closer

now it dont look like lack of oil:face-icon-small-blu, looks like something came apart.....its tuff to say what came apart first, id check the shaft play first

then completely disassemble the engine and shaft for a very extensive inspection for debris that will only make it fail in a couple miles after you slap new parts in it

bart0678 · May 18, 2010

pull it down and check for a leaking base gasket.

AKSNOWRIDER · May 19, 2010

are the ring pins(stops) still in place or missing?, another sign of deto if they are loose or gone...

03rmking · May 19, 2010

AKSNOWRIDER said:
are the ring pins(stops) still in place or missing?, another sign of deto if they are loose or gone...

They are still in place.

SnowDevil · May 19, 2010

Did you get 2010 pistons or 2008? there is a difference and the 10's are not as strong.

mattymac · May 19, 2010

03rmking said:
Yes our fuel has ethanol. But it also did last season. No change in the fuel it's been burning for 2000 miles. I was in Revy when it happened. Started the day burning Idaho fuel, dumped my 5 gal of Canadian 94 octane and this happened few hours later.

You didnt factor in the exchange rate for the can 94 octane!

No signs of deto to me, catastrophic IMO.

JSCC · May 19, 2010

mattymac said:
You didnt factor in the exchange rate for the can 94 octane!

No signs of deto to me, catastrophic IMO.

Agreed!
Check the cylinder to see if it is still round.

Piston skirt came apart (pics)

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