Cylinder Question

[Big Woody]

I finally pulled the trigger on a compression tester and was testing all my chainsaw and other 2 cycle engines tonight. I also bought a little LED flexible light at lowes which fits in the spark plug hole and you can really see the cylinder walls well.

Anyway I was looking in my 2 cycle 1 man General auger cylinder and noticed a black streak up the cylinder wall about 1/4 inch wide. Upon further inspection I notice the exhaust had two ports and the black streak lined up with the cylinder strap between the two exhaust ports. It seems to be carbon since I could lightly scratch through it with a tiny screw driver.
The black streak went up as far as I could see and continued down between the exhaust ports.

I was wondering what might be causing this and if it is a serious problem. It only gave about 110 psi compression but it runs well and digs an 8 inch hole with no problem. It has a tecrapseh motor though.

 

[bwalker]

It sounds like the piston seized on the exhaust bridge at one time or another.

 

[Big Woody]

Thanks Ben.

I may pull it apart after using it a bit more and rebuild it for experience. I guess thats the price you pay for buying Home Depot used equipment.

I also bought a Makita DCS 6401 for $200 from HD rental and had to replace all three clutch springs. They were stretched so bad it was pittiful but they told me nothing was wrong with it. It leaks oil like crazy out the pump when sitting around as well but suprisingly it has 160 psi compression. Came with a new 20 in bar and chain and cuts real strong. I'm done buying their use junk.

 

[ErrolC]

Its possible but I would be skeptical about any seizure unless the cylinder on the exhaust side is scored above the port itself as well..these run an ali cylinder and chrome ring..if the cylinder is reasonably clear of scoring (there will typically be light sandpaper like scuffing) then it would most likely be typical wear ..if or when you take the cylinder off, and a partial seize has happened at some time you will see small grainy chunks out of the piston..if not put in a new ring (I clean the cylinder and piston with paint stripper to clean away carbon without marking the walls, and hose it off). should do the trick!