What's on your bench today?

[rob,s]

New pot and piston ran for a few minutes then stopped and lost compression. Leave scoring to the sides of the pot and piston. What could have caused this?

[rob,s]

Picture 2

[rob,s]

Picture 3

[Eddy_t]

Could be a faulty decomp valve, a sharp edge on a port, poor honing and a bulge in the cylinder, bit of grit in the cylinder, could be any of a long list of things

 

 

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[Ryan]

Another one I have seen a couple of times is a crankshaft bearing cage breaking up.

[windy81]

Fault finding an almost new MS180 today that wont start. Quick compression check gets 90psi. However the piston looks good, virtually new from intake and exhaust ports.

 

Tear it apart to find the big end bearing has disintegrated caused presumably by the engine pan decomposition from sitting for quite some time.

I presume that the alcohol in the fuel ate away at the engine pan and the resulting debris which felt very gritty almost like sand basically, acted like grinding paste and broke away the big end bearing and from there the rollers got trapped in the transfers and all hell let loose.

 

Apart from that the saw has only been used 3 times.

First time i saw fuel damage like this and i'm really considering 2 -stroke oil that has fuel stabiliser in it such as the Amsoil Saber Professional.

[Dinosaw]

I don't like the look of what appears to be two bits of metal embedded in the squish band in Pic 2.......

[windy81]

ye looks like there is a lot of grit there

[GardenKit]

Fault finding an almost new MS180 today that wont start. Quick compression check gets 90psi. However the piston looks good, virtually new from intake and exhaust ports.

 

Tear it apart to find the big end bearing has disintegrated caused presumably by the engine pan decomposition from sitting for quite some time.

I presume that the alcohol in the fuel ate away at the engine pan and the resulting debris which felt very gritty almost like sand basically, acted like grinding paste and broke away the big end bearing and from there the rollers got trapped in the transfers and all hell let loose.

 

Apart from that the saw has only been used 3 times.

First time i saw fuel damage like this and i'm really considering 2 -stroke oil that has fuel stabiliser in it such as the Amsoil Saber Professional.

Far better to use Aspen in a saw that gets used as seldom as thst one.

[wisecobandit]

Fault finding an almost new MS180 today that wont start. Quick compression check gets 90psi. However the piston looks good, virtually new from intake and exhaust ports.

 

Tear it apart to find the big end bearing has disintegrated caused presumably by the engine pan decomposition from sitting for quite some time.

I presume that the alcohol in the fuel ate away at the engine pan and the resulting debris which felt very gritty almost like sand basically, acted like grinding paste and broke away the big end bearing and from there the rollers got trapped in the transfers and all hell let loose.

 

Apart from that the saw has only been used 3 times.

First time i saw fuel damage like this and i'm really considering 2 -stroke oil that has fuel stabiliser in it such as the Amsoil Saber Professional.

 

Ive done about 3 newish (2009-2010 ish) saws all with the same issue albeit the 210/230/250 range.

As a matter of interest does the 180 have a sort of integral built in small end for want of better words? IE you cant swap the bearing as its part of the con rod/crank?

 

The earlier ones never had this or any common issue with big end failure. Certainly on the 210-250 range the earlier crank with separate small end bearing is interchangeable with the revamped version.