Blown up 700 Triple

musselman

musselman

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Sunderland, Ontario
Don't know what happened here guys, could use some help. It was about 0 deg C out that day so pretty warm, sled has run in -20 this season already. Sounded like a plug starting to foul then eventually lost the cylinder completely. Here are a few pictures of what happened. Does the wash look ok or is it too lean? It doesn't look like there is any melting of the piston but it's hard to tell.

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Lean

To me it looks too lean, nothing more. Don't see any signs of detonation...just way too lean. Now, I'm not an expert by any means.....I'm sure some people with far more knowledge will chime in.

Madmatt
 
Is that the clutch side musselman?? Mine did same thing when my crankseal shit the bed. She was still runnin on two lungs and probably got home with it didnt you..
 
HI MATT, THIS IS WHAT I THINK. ALOT OF DAMAGE THERE. LOOKS LIKE BLOWBY ALSO. AT ONE TIME YOUR WASH WAS PERFECT. BUT LOOK HOW YOUR OUTER EDGES ARE GREY ON THAT PISTON TOP. THE HEAT FROM THE MELT DOWN WENT INTO YOUR RING LANDING AND THERE WAS NO WHERE FOR YOUR RING TO GO THATS WHATS CAUSED MOST OF YOUR DAMAGE. THIS SLED GET HOT OR OVERHEAT ? 3:16 (yammie tony)
 
This did have a tank of bad gas run through it, it's my buddies sled and we filled up at the same station. I noticed my sled was idling high and the dcs light was coming on but I think he might had done the damage already. since it blew it had about 4 tanks of good gas run through it so it should have been fine.

The reason that there is so much damage and blow-by there is because he kept running it after it lost the cylinder for about 15 km, he thought it was just a plug.

I will post up the pics of the other pistons, I think the wash is a bit lean on them too.

the cylinder was the clutch side as well. Thanks guys really appreciate it, just want to find the root cause before it goes back together.
 
yami1 said:
Is that the clutch side musselman?? Mine did same thing when my crankseal shit the bed. She was still runnin on two lungs and probably got home with it didnt you..
Click to expand...

x2 my 86 polaris died of a bad pto crank seal.

what do the plugs look like? Are there any mods to the sled that would effect jetting? Does he run any kind of ethanol treatment?

the manual say 88 or higher for my 02 mm and I'm running 91+ just to be safe
 
Has he gotten into the carbs yet? That carb might have gotten some junk into it from the bad tank and leaned it out. If the other 2 jugs look good I'd suspect the pto seal/plugged jet.
 
tedgoesfast said:
looks to me like the pin let go and ring turned and caught port how many miles on sled
Click to expand...

I agree the ring probably turned (probably on the ride back) and caught a port but after melting on the crown from a lean condition. I agree to check the carbs and the crank seal.
 
I should list off the mods done to it:

-1 layer head gasket
-reed spacers
-boost bottle
-drilled stock can

It also has the stock jetting.
 
I think I will put full head gaskets in there and bump up the needles one clip since this happened about 1/4 to 3/4 throttle. With the normal head gaskets bad gas won't be such a huge problem and it seems to be rather common.

Here are pictures of the other 2 pistons, they do look a little lean to me:

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broken ringland?

Hi,

This is my .02 everything posted so far still DOESNT explain that broken ringland on the left side of pic/piston & carbon /sout behind it that says the ringland has been damaged for some time just hadent craked all the way through to separate from the piston

I can see the peice that I am talking about (ringland) "walked" up & down pushing on the top ring causing the damage to the top ringland / dome area on left of piston

Call me crazy but thats the story I see


Jay
 
jaybirde978 said:
Hi,

This is my .02 everything posted so far still DOESNT explain that broken ringland on the left side of pic/piston & carbon /sout behind it that says the ringland has been damaged for some time just hadent craked all the way through to separate from the piston

I can see the peice that I am talking about (ringland) "walked" up & down pushing on the top ring causing the damage to the top ringland / dome area on left of piston

Call me crazy but thats the story I see


Jay
Click to expand...

I see what your saying about the soot/carbon behind there with fresh looking break on side of it. It entirely possible that may have had cracked and weakened it, bad gas lead to lean that made issue worse and finally became a real issue when cylinder went down. Keep in mind he stated they rode sled an additional 15km after cyclinder went down. Its also entirely possible that the fresh looking broken part could have ben broke tearing it apart.
 
How many miles on her mussellman?? Bout 8-10 thousand miles and them crankseals go bad on those red heads. thats what i think. Like I said before looks exactly like what happened to me on a 97 sx I had. Your gonna want to split case and peek in there and make sure crank bearings are good and clean any debris outta their. With all that damage something had to fall down in there
 
musselman said:
This did have a tank of bad gas run through it, it's my buddies sled and we filled up at the same station. I noticed my sled was idling high and the dcs light was coming on but I think he might had done the damage already. since it blew it had about 4 tanks of good gas run through it so it should have been fine.

The reason that there is so much damage and blow-by there is because he kept running it after it lost the cylinder for about 15 km, he thought it was just a plug.

I will post up the pics of the other pistons, I think the wash is a bit lean on them too.

the cylinder was the clutch side as well. Thanks guys really appreciate it, just want to find the root cause before it goes back together.
Click to expand...
From what I can understand from the mods you mention, you blew up a SX triple? That sled does not have the DCS.
 
Yes I have an 02 srx and my buddy has my old 700 red head engine.

The engine had about 15000 km on it but the pistons only had 1000 km.

Do you guys think the other 2 pistons are on the lean side?
 
Yup the other two domes look really lean to me. No wash to speak of. I'd be checking the screens under the inlet needles. fuel today sucks, you wouldn't believe some of the growths I've found in the bowl area.
 
Checked the carbs last night and they were spotless. Going to run full head gaskets and I richened the needles 1 clip so we'll see how it goes.
 
I also saw last night that the choke was adjusted way to tight and stuck open almost the same amount as half choke. Don't know if that would cause any problems other than a rich condition.
 
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