burnt piston detectives step inside.

jethrobodean · Feb 11, 2015

07 CF1000, 09 reflash, 5k miles, NO Mods, all stock. Been opened up before me when I bought it at 2k. Has PTO written on the side of the cylinder in marker. Traveling 60-70 MPH for 2 miles, pulled to stop, shot off trail to the side and eased back on trail. Sled slowed and died like it ran out of gas. Knew I was in some kind of trouble because the sled never dies.the sled wouldn't start. Pulled the plugs and both electrodes on the PTO side were bent closed. the plugs were good color. They had little pieces of marbles on the inside which were not a good sign. Held thumb over the hole of the cylinder and found no compression.got her home, thankfully for backup sled I had my ride for the weekend. But this is what I found. You guys please help me determine what the hell happened so it doesn't do it again. Pictures will follow after I upload them

[/URL][/IMG]

jethrobodean · Feb 11, 2015

[/URL][/IMG]

jethrobodean · Feb 11, 2015

The mag side piston

[/URL][/IMG]

jethrobodean · Feb 11, 2015

What happened? fuel? air leak? Chunk of something? I was running 91 octane and riding sea level. Stock sled no mods. The gash on the piston was on the inside, PTO intake port. I am going to need another jug if anybody has one to sell.

kiliki · Feb 11, 2015

looks like bad/old fuel to me with the end result det. with the plug ground straps shut is a side affect sometimes it will break them off or brake the ceramic part of the plug as well as make the loose.
I do have a good used jug shipped to?
Was the tps plugged in?

also looks a little dry on top of the piston was this the first ride of the year?

ACMtnCat · Feb 11, 2015

What's up with the lower ring gap? Did the ring spin out of place?

jethrobodean · Feb 11, 2015

The rings are welded / pinched in the grooves. the locating pins are there. topped off in the morning and traveled 60 miles before this happened. Drained tank yearly and start fresh. the day before rode 100 miles no prob.
TPS plugged in. running 91 octane
Shoot me a price shipped to 53545.

We were running a sugary snow trail for miles and my intake was eating alot of snow. When I dropped off trail the nose of the sled went down and then climbed back up onto the trail, instantly my sled died. Water dumping into the throttle bodies?

jethrobodean · Feb 11, 2015

It where bad gas, How come only one side was damaged? Antifreeze leak between the case halves on the mag side cause this? Ant freeze leaking into the bottom half being pulled up into the piston?

kiliki · Feb 11, 2015

defiantly could be antifreeze or water ingestion. was the coolant bottle full before you took it down?
as for the ring stuck in the grooves this is common on a FUBAR piston, and the location pins are all still in place?
the other question is if you did a lot of miles the day before then what changed to let snow in?
it looks like it was getting oil because the sides didn't' have the smear real bad.

jethrobodean · Feb 11, 2015

coolant bottle was full. Just do not understand why just one side detonated and the other is good. Can I run the head with the pits in it?

kiliki · Feb 11, 2015

you can but make sure you get all the loose derbies and smooth it out ever so gently as to not mess with the squish too much. best is pick one up off ebay for around 100. yours is on the rougher side or what i would even consider to run. you are close to millennium technologies might look at an exchange on the jug from them.
as for the fuel did you get it from a know good station?

jethrobodean · Feb 11, 2015

Gas station in a large town. ( Iron Mountain, MI) burned through a half a tank before she let me down. Upon further investigation I see a chip or two on the Mag side piston edge. Blow bye brown underneath both pistons. Ordering new Oem pistons and gaskets. Is it necessary to replace the wrist pins and bearings when doing a top end? I do nothing but trail ride, No long heavy pulls. I expect that I should. I just do not want to throw more money at new part unless I am certain what caused the original failure.

jethrobodean · Feb 11, 2015

Blow bye leading to detonation? brown carbon below the rings?

jethrobodean · Feb 11, 2015

Figured it out. Old pistons, chunk of the corner broke off, seizing the rings on that side, excessive blow by = detonation of the top of the piston from a pre lean condition. that's why the other side (mag) is good beside acouple of small chips from the edge. Cleaned up the scars in the jug with a emery cloth and gonna run it again. New Oem pistons and bearings ordered. I think I came out lucky. I knew I should of done the pistons prior to this season, I thought I could get another season out of her. Oh live and learn.

Thunder101 · Feb 12, 2015

I'm going with deto from old or bad gas. And it is very common when this happens it takes down the "hot" side. To me it looks like the mag was very close to as it shows light signs of deto. Saying you we're cruising for two miles at 60 right before also leads me to this .

Snow ingestion will wash your oil off the intake skirt not sand blast the piston crown/edge.
Get some new parts and I'm sure everything will be back to normal. With pump fuel there is always the chance your not getting the octane your paying for and the chance of high ethanol which attracts water which displaces fuel both make things leaner then fuel with out ethanol.
Approximately 5000-6000 rpm will be the hottest part of the timing curve so I would try to not cruise in that range.

jethrobodean · Feb 12, 2015

Run it or replace it.

[/URL][/IMG]

boondocker97 · Feb 12, 2015

Thunder101 said:
I'm going with deto from old or bad gas. And it is very common when this happens it takes down the "hot" side. To me it looks like the mag was very close to as it shows light signs of deto. Saying you we're cruising for two miles at 60 right before also leads me to this .

Snow ingestion will wash your oil off the intake skirt not sand blast the piston crown/edge.
Get some new parts and I'm sure everything will be back to normal. With pump fuel there is always the chance your not getting the octane your paying for and the chance of high ethanol which attracts water which displaces fuel both make things leaner then fuel with out ethanol.
Approximately 5000-6000 rpm will be the hottest part of the timing curve so I would try to not cruise in that range.

I'm with Thunder on this. Injector possibly even started freezing up on that side as well? Age/fatigue on the piston couldn't handle it anymore and your chip probably came off as a result. Not much carbon on that mag piston crown either with small amount of wash. Maybe running a touch lean overall? Got a picture of the underside of the pistons? Light color there is ok, but if it is dark or has deposits then it was on the lean side and actually getting hot enough on top to transfer through to the bottom and start cooking fuel to the underside surface. I know the 09 maps are leaner than the 07s. Got a shot of sub-grade ethanol fuel matched up with the lean mid-range 09 map and it was probably right on the edge until it finally went down.

If I spent the money on new pistons, I would spend the extra $250 for a re-nik cylinder too.

jethrobodean · Feb 12, 2015

burnt piston underside.

[/URL][/IMG]

good side

[/URL][/IMG]

Thunder101 · Feb 12, 2015

Replace both pistons and pick up a used or replated cyl and it looks like your head is done.

boondocker97 · Feb 12, 2015

When I was talking to Dale Cutler a few years ago, he told me too much color under the pistons is one of the signs he looks for when diagnosing a motor that went down. Tattle tales if the motor had been running lean. By the amount of actual carbon on yours, I would guess it was running on the lean side for a while. How many miles have you put on since you bought it at the 2K mark? Running ethanol blended fuel (contributes to the lean condition if not adjusted for)?

burnt piston detectives step inside.

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Similar threads