anyone had this happen before 2nd try

[logcutter429]

oops wrong pic good picture of my daughter though

 

[Rotax Robert]

hmmmm, maybe a crank seal (vaccume leak). I am assuming that the rod and piston were still hooked together. Never had one go like that though, just a seaze or two

 

[eyolf]

I've seen that on snomobile engines before.
Anybody remember the old 3 cyl Hirth free-air engines, or the bigger Sachs twins?

 

[logcutter429]

It didn't hurt any of the rebuild job everything was still intact, it started sucking air and i shut it down.

 

[buckwheat]

Was the pin bearing between the crank and the piston still in one piece? If not, there could have been enough play to cause the piston to jamb against the cylinder wall and blow it out.

 

[logcutter429]

yea, ihad it put in new with the rebuild job , didnt hurt it neither.

 

[Dennis]

What that blowout looks like to me is one of two things....A: loose head bolts...or B: foreign material.....are there any marks on the top of the piston? This happened to a 394 that I had a pipe on....small "peen" marks on top of the piston made me believe that something got into the saw and literally knocked it loose...and broke out the bottom corner of the cylinder.

 

[Weatherby]

A little JB Weld and that cylinder would be good as new. Never seen anything like that, and I hope I never do.

 

[Dennis]

LMAO....ask Rotax about his JBWeld experiences...I have a 394 with an 084 carb that someone jbwelded to it....imagine that...its the same saw I was referring to above...
I know you were kidding Weatherby...but it just brought back memories..
Now duct tape...that is different....

 

[bwalker]

I had the same thing happen for no apparent reason on a sled motor. I had a very good welder I know tig it back together. I put another 1500 miles on that motor and sold it to a buddy that rode it another year without failure. That being said I would get the thing welded unless you have access to a cheap cylinder.

 

[logcutter429]

Well the head bolts were tight and we looked at the piston, since it was new nothing there, had us all confused too, i found a jug that was about new and fixed it.

 

[glens]

Maybe it was just a Monday morning or Friday afternoon casting?

What do you think, Fish?  Maybe it was just a freak occurrence of predetonation or some tangential force affiliated with lack of Marvel Mystery Oil use?

:<tt>)</tt>

Glen

 

[dozerdan]

How could you possibly get a barrel that dirty in only one week of use?
Dan

 

[wmthrower]

eyolf,

You must be refering to the "Honker" 793cc. I know of the big Sachs twins too. never quite seen that on them though.

 

[logcutter429]

I dunno i use em pretty hard, they did clean it up before the rebuild, cut alot in the rain seems like gunk builds up alot more in them conditions.

 

[John in MA]

Originally posted by Dennis
Now duct tape...that is different....

The handyman's secret weapon!

 

[oakman]

i had this exact looking thing happen to a 1974 honda cr250 dirt bike that sucked in a small amount of water, going through a creek. upon dissassembly, there was maybe a quarter cup of water in the bottom end. you mentioned you cut in the rain alot. could this possibly have hydraulic locked, somehow? just a wild guess. my other wild guess is a flawed/previously cracked casting, and with the rebuild, the higher pressures simply caused the failure.

 

[Tony Snyder]

I think water in the crankcase did it.

 

[logcutter429]

If its water in the crankcase now that it is up and running again, could it happen again?

 

[My2cents]

All you needed for that fix was a little heat resistant Super Glue. I believe if you read the package it says "Bonds to Metal".You wouldn't have even had to take the jug off!