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Blown piston....why?

Jonathanpitzl

Jonathanpitzl

Member
Lifetime Membership
So I was riding my new sled and about 6 miles down the ditch in plenty of snow the exhaust side piston went out. It's an 06 crossfire 700 with ported cylinder, rumble pack can. And oil delete. I mixed the oil at 32:1 using amsoil interceptor synthetic. I had 72 gram cutch weights and was giving her nuts at 1100 ft altitude. And part of the piston broke off. It still runs.

Would the piston pieces just plot out the exhaust?

Do you think there is any cylinder damage and what do you think cause it? Should I keep it after fixing it or get rid of it?

Here is a pic and thanks for the help!

http://s1186.photobucket.com/user/jonathanpitzl/media/Mobile Uploads/image-6.jpg.html?sort=3&o=0
 
Did you have fresh fuel in the sled?
Looks like detonation started the problem. So if you had old fuel or with the porting and other work if you ran a low grade unleaded fuel it may have detonated.

Pull it apart, make sure the rod isn't bent, put on a new cylinder and new piston, wrist pin, bearing etc. and run it.

Make sure you flush the heck out of the case, I am sure some parts are floating around in there.

I am sure a lot of guys would just do a total rebuild, IMO if you just want to take a chance do a top end. (I have done it numerous times and worked out just fine)

Thunder
 
Are you shure you mixed that tank. How long did you let it warm up.
I'm shure the cylinder is toast, look at the head also . At least it was the top of the piston lucky you, not a skirt. pull the head and cylinder and send us a pic you might be able to use some acid and a razor blade on the cylinder and get the aluminum off and hone the cylinder. "MAYBE"
 
Took it out of the shot and let it idle for about 7 minutes the took off idleing it a half mile out of town because of the loud exhaust
 
was your power valve hitting the piston..??..if a fuel issue or mixture you should have issue that would be visible on other cylinder...maybe you just snagged a badly ported port..
 
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I'll have to see about the valve, and the other piston was the same as it was before, could the 72g clutching have to do with it? I was give her nuts pretty good
 
did you just rebuild the motor? the locating pin is in the exhaust port indicates the pistons are installed backwards
 
Damn dude that sucks. I know you just got that thing.

But that looks violent and highly mechanical, like something very much in the way of the piston moving. Just because it's easy to do I'd go pull the power valve on that asap and see what it looks like. It looks like from the other pics in your photo site you were messing with the cable servo?
 
X2 on backwards pistons, the gap in the ring should be 180 degrees from where it is, looks like it caught on the exhaust port coming back down and pulled up and slowly crushed that part of the piston till it gave out. There is a dot on top of the piston, is it facing the front or back of the sled in your engine?
 
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I realize that, the ring gaps would be closer to the outsides of the exhaust hole.
 
Piston is in backward man...that sucks, we've all done it at some point, some are luckier to catch it and some aren't! I would get a new cylinder and piston/ring kit, clean out the bottom end, and throw it back together. Surprised it lasted for 6 or 7 minutes running that way!
 
 
You can't hone it, it needs repair and replating. Millenium would have you a rebuilt one in two days. Your pics did not show the top of the piston, was it pitted from deto? It also looks like the power valve was just cleaned, was it in the right way?
 
Cable adjustment would not of had anything to do with the valve hitting the piston. I see the bottom ring is broken but the top one is just bent. ring could have broke and caught the port on the way down. Doo had a problem with the early 800 engines breaking the tops off like that, they finally blamed it on the ring groove being too close to the top of the piston. A water droplet getting in there will blow a piston apart too.
 
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