Cracked Cylinder - Any idea why?

[boltonranger]

This is a cylinder from a Homelite Vac-attack II approx. 7 years old. I realize not a saw, but it is a 2 stroke.

Blower is the handheld variety, always run at 32:1.
Was a little "wonky" last couple times of use - I figured maybe time to gumout the carb; but once warm ran off choke alright; though a little hesitant to rev at first. Last time out - it quit while running. semed like it was running hotter and the revs slowed some at wot and exhaust sounded "different".
Gas was low so I didn't think much of it
Next I tried to start - would not run and again sounded different when pulling starter - different exhaust note.
Hmmmm. Pulled muffler; looked ok inside. Pulled crankcase cover and noticed something strange. A crack in the cylinder below the exhaust port! So I don't know if lean running can even do this or if it was defective casting.
See pic below.(Notice the crack near the base)
Anyone else ever have this happen?
Really not sure why it happened.
-br

View attachment 259126

 

[mattinky]

What's the piston look like?

 

[Stem450Husky]

pull the jug off, im interested to see (if) how bad the piston is scored opcorn:opcorn:

 

[fastLeo151]

Maybe its just a cheap blower?

 

[boltonranger]

Ok I just removed the cylinder and the piston and cylinder are really clean.
No significant scoring on either; some light scratches on the piston that you have to hunt for to even see.
So I'm left with..what?
It's an inexpensive blower?
That I already knew.

But my question was - - Have any of you ever had this happen?
I don't believe it was a lean condition that caused it.
I think the lean condition was caused by it.
Just looking for answers if they're out there...
-br

 

[Arrowhead]

My guess is factory defect. Most likely the bottom of the jug or the top of the case were not machined perfect. It looks like the mounting "ears" of the jug are quite long. It's always best when the cylinder bolts are closest to the bore opening. Expansion and contraction over a few years probably made it finally brake. Also could have been a casting impurity in the jug, or simply a piss poor design. Whatever the case, it was not operator error.

You can probably get away with cleaning the crack with a small wire brush and carb cleaner, then use JB weld. I wouldn't apply the weld until it's all bolted back into place. I believe that would work fine. New parts are probably more than the unit is worth.

 

[Stem450Husky]

more than likely just a casting flaw and the way it was set up when it was machined probably has something to do with it. I'm a machinist and do a lot of casting work (large centrifugal pumps). You wouldn't believe how many junky castings we get here.

 

[Fish]

Looks like damage from using ether or a real volatile carb cleaner.

 

[boltonranger]

Looks like damage from using ether or a real volatile carb cleaner.

Yes I agree it does appear that way;
but no, it's always started on it's own.

Never used ether or CC in it.

Pretty good guess though.
-br