Two Stroke Piston/Ring/ Cylinder Damage Causes

[Mek-a-nik]

I diagnosed an older Echo SRM2400 today, it wouldn't start.
It only had 80# of compression and the piston, rings and cylinder were visibly scored, as seen through the exhaust port.
It got me to thinking as to what the reasons are for this. The only ones I can think of off the top of my head, are using the wrong oil, not enough oil or none at all.
What else contributes to this?

[KE4AVB]

Foreign materials inhaled, hard carbon deposits, running too lean are few that I can think of beside the ones you listed already.

[bgsengine]

Air leaks, overheating, low quality fuel (Stale gas), water in gas, and excessive RPM (Running engine at full throttle with no load) to add to that list.

*Edit to add*

By the way, an experienced eye can tell just from the damage seen , which of the causes would be most likely - Even though a lean seizure and a overheat seizure may look almost identical, for example , there are further clues to tell the tale. next step after seeing that damage through muffler hole should be a crankcase leakdown test and fuel system pressure/vacuum test , before further tear down.. otherwise you might fix the symptoms but not the cause..

[Luffydog]

Brand new one came back the other day man was cutting cedar had only for about 4hrs and quit. Come to find out muffler was loose and suck the dust right in and locked it up.

[Arkie]

Brand new one came back the other day man was cutting cedar had only for about 4hrs and quit. Come to find out muffler was loose and suck the dust right in and locked it up.

Hum:
You sure cedar dust was getting in thru the muffler port while it was running??? Is this really possible???

Sounds more like the air filter assembly maybe not sealed good?

Respectfully

[bgsengine]

Is this really possible???


Respectfully

Yep. its a 2-stroke - leaking muffler gasket you can get dirt in that side too - you have to remember they are open port so when piston is on the way UP (compression stroke) it's gonna have exhaust port open and crankcase *vacuum* that can suck in dirt from the exhaust if the gasket is not sealing it won't have the "suction" of the exhaust gas leaving the muffler to scavenge loose carbon.dirt and other deposits, which means the crankcase vacuum will do that instead - bringing the debris into contact with the piston and cylinder.. - so muffler gasket is a VERY important part of the whole system.

[KE4AVB]

Yep keeping muffler gaskets and muffler tightly sealed are even more important on those plastic crankcase models too or you will have a thermal nuclear meltdown.