[YukonWild]

Alright, burned my sled down a couple of days ago, 1 cylinder is fine, the other.. well. Just want to know what you guys think, and what you think caused this. The lighter colored side of the head is the side that burned down.
[attachment=60883SCF02981.JPG][attachment=60884SCF0300.JPG][attachment=60885
SCF0310.JPG][attachment=60886SCF0308.JPG][attachment=60887SCF0309.JPG]

 

[cmscat50]

Where's the piston?

 

[YukonWild]

Piston is still inside the cylinder, I only had a couple hours yesterday to take the motor out and stuff, so I didn't get it completely tore down.

 

[chevymx78]

well u said the lighter one is the one that burnt down, lighter=leaner, prolly was too leaned out ?

 

[cmscat50]

Take a picture of the piston. No way to tell without it.

 

[Jeff H]

And also a shot that shows the entire cylinder wall. Taka a picture of the underside of the piston dome too.

 

[YukonWild]

Ok, have some more pictures on my cell phone, will get them posted up tonight.

 

[YKmark]

if you were riding in that cold snap last week without re-jetting, you probably fried it there. i had to rich up my dads powder special 700 ALOT for a ride last weekend (went from 0 celsius to -30 celsius). If not, i could be anything from debris and crap clogging a jet in the carb to fragments in the case from a broken piston or pin or something else foreign. Big pistons require big warmups and lots of fuel, if your jetting was off or you didn't let it warm up properly, you can fry a piston in those bigs cats. I cold siezed my 02 800 mountain cat once by being stupid and not letting it warm up properly and it was actually pretty warm outside... like the others said, get the other pics up and you should be able to tell, but those would be my guesses. :beer_cheers:

 

[YukonWild]

<div class='quotetop'>QUOTE (YKmark @ Jan 18 2007, 10:10 AM) <{POST_SNAPBACK}></div>

if you were riding in that cold snap last week without re-jetting, you probably fried it there. i had to rich up my dads powder special 700 ALOT for a ride last weekend (went from 0 celsius to -30 celsius). If not, i could be anything from debris and crap clogging a jet in the carb to fragments in the case from a broken piston or pin or something else foreign. Big pistons require big warmups and lots of fuel, if your jetting was off or you didn't let it warm up properly, you can fry a piston in those bigs cats. I cold siezed my 02 800 mountain cat once by being stupid and not letting it warm up properly and it was actually pretty warm outside... like the others said, get the other pics up and you should be able to tell, but those would be my guesses. :beer_cheers:[/b]

Jetting should have been really close, I have the holztman ATTAC and it was set for as cold as -35, and the temp when I cooked my engine was -20 or so.

 

[YukonWild]

[attachment=61111SCF0297.JPG][attachment=61115SCF0308.JPG]
[attachment=61114SCF0305.JPG][attachment=61116SCF0310.JPG]
[attachment=61109SCF0286.JPG][attachment=61110SCF0295.JPG]
[attachment=61113SCF0300.JPG][attachment=61112SCF0299.JPG]

Here is a bunch of the pics you guys were asking for, let me know.

YW

 

[YukonWild]

Does it look to you guys like I squeeked it? I am hoping that's what it is so it does not happen again. I would like to add that I did not warm the sled up for a very long time before I started riding.

 

[ZRlover--off]

cold sieze?

 

[scrat600]

I would guess cold seizure too.

 

[CFM-Z440]

Look at the piston crown. No wash at all! LEAN

There is a very small amount of wash on the better piston. I wouldnt call it a cold score because it was too lean to live no matter what happened. I would say that it was way lean, but didnt have wide open throttle long enough to start detonating or to blow a hole in it.

Kind of looks like a possible lubrication problem also. Maybe caused by the excessive heat.

I dont think it is a cold score because it is all the way around. Cold scores are usually found in the "four corners"

Hopefully your rods arent blue where the wrist pin bearing goes. $$$

 

[6Mile]

<div class='quotetop'>QUOTE (CFM-Z440 @ Jan 18 2007, 11:58 PM) <{POST_SNAPBACK}></div>

Look at the piston crown. No wash at all! LEAN

There is a very small amount of wash on the better piston. I wouldnt call it a cold score because it was too lean to live no matter what happened. I would say that it was way lean, but didnt have wide open throttle long enough to start detonating or to blow a hole in it.

Kind of looks like a possible lubrication problem also. Maybe caused by the excessive heat.

I dont think it is a cold score because it is all the way around. Cold scores are usually found in the "four corners"

Hopefully your rods arent blue where the wrist pin bearing goes. $$$[/b]

Exactly,

This is why I think there are a couple of issues that have compounded and caused the failure. First is a Lean fuel mixture in the mag cyl that failed. The second is a lack of lube. both sides are showing signs of this. Look at the "good" piston on the exhaust side, there is scoreing there as well.

Lean Fuel and lack of oil = squeeeek

Resolution:
1. Replace parts as needed
2. prelube cyls and crank put back together with out the carbs installed. Start to clean the carbs.
3. Blead the oil pump
4. put drill with socket adaptor on clutch bolt. and turn over crank and verify that the oil pump is pumping oil to the intake boots.
5. If not blead the pump and repeate #4.
6. Clean the carbs again.
7. install carbs and run it with 50 or 75 to 1 premix in the gas. ( Plugs are cheep)

 

[YukonWild]

<div class='quotetop'>QUOTE (6Mile @ Jan 19 2007, 01:48 PM) <{POST_SNAPBACK}></div>

<div class='quotetop'>QUOTE (CFM-Z440 @ Jan 18 2007, 11:58 PM) <{POST_SNAPBACK}>

Look at the piston crown. No wash at all! LEAN

There is a very small amount of wash on the better piston. I wouldnt call it a cold score because it was too lean to live no matter what happened. I would say that it was way lean, but didnt have wide open throttle long enough to start detonating or to blow a hole in it.

Kind of looks like a possible lubrication problem also. Maybe caused by the excessive heat.

I dont think it is a cold score because it is all the way around. Cold scores are usually found in the "four corners"

Hopefully your rods arent blue where the wrist pin bearing goes. $$$[/b]

Exactly,

This is why I think there are a couple of issues that have compounded and caused the failure. First is a Lean fuel mixture in the mag cyl that failed. The second is a lack of lube. both sides are showing signs of this. Look at the "good" piston on the exhaust side, there is scoreing there as well.

Lean Fuel and lack of oil = squeeeek

Resolution:
1. Replace parts as needed
2. prelube cyls and crank put back together with out the carbs installed. Start to clean the carbs.
3. Blead the oil pump
4. put drill with socket adaptor on clutch bolt. and turn over crank and verify that the oil pump is pumping oil to the intake boots.
5. If not blead the pump and repeate #4.
6. Clean the carbs again.
7. install carbs and run it with 50 or 75 to 1 premix in the gas. ( Plugs are cheep)
[/b][/quote]
Thanks for the advice. The only thing that is making me wonder about being lean is that I have driven about 300 miles on this sled so far this year and I didn't change a thing between the first ride and the last. And the other times I was riding I was wide open throttle for minutes at a time.
I have an older friend doing the work for me, so I'll show him this, and see what he thinks.

 

[94ZR580]

Maybe it was colder this time that the other days you were riding? Maybe you had some water in the gas on this day? Could be lots of reasons why it went lean this day when it was fine the day before.

 

[YukonWild]

<div class='quotetop'>QUOTE (94ZR580 @ Jan 19 2007, 03:01 PM) <{POST_SNAPBACK}></div>

Maybe it was colder this time that the other days you were riding? Maybe you had some water in the gas on this day? Could be lots of reasons why it went lean this day when it was fine the day before.[/b]

That's the kinda thing I need to know, if I should just leave my setup the way it is, or readjust everything and richen the fuel mixture, etc.