Horizontal scratches in cylinder wall?

MrGiggles · Aug 19, 2009

This isn't chainsaw related, but maybe you guys can help me out.

I bought a Troy Bilt 4 Stroke trimmer in 2006. I didn't research before I bought like I should of, but it worked flawlessly for 3 years. Easy to start, and it ran very well. Around mid this summer, it started making a noise at idle. Like a tapping noise that would drag down the engine and stall it. I looked at it once and couldn't find anything out of the ordinary so I continued using it. It got worse and worse until it stopped working completely because it would not run and was partially seized. Upon tearing into it nothing seemed out of the ordinary. Everything was in very good shape. Except the cylinder. There is a 1/2 strip of random gouges mid way into the cylinder wall, They are very deep, probably around 1/32" of an inch. It goes all the way around the cylinder as well. This has us puzzled.

Maybe the coating of the cylinder flaked off? The second compression ring on the piston was broke as well, but that would cause vertical scratches correct?

I would take pics my camera batteries are dead. :clap:

On the positive side, I replaced it with a Stihl FS90R. No comparison between the two. I love it.

dragrcr · Aug 20, 2009

piston slap or (rock) skirts worn down and piston rocks in the bore, especially when cold as aluminum expands more that steel, so the piston will be even more loose on cold start, then run under load before warmed up. a;so usually makes a interesting egg shaped mark on the skirt

wigglesworth · Aug 20, 2009

Let me pioint out the first mistake.......

MrGiggles said:
Around mid this summer, it started making a noise at idle. Like a tapping noise that would drag down the engine and stall it. I looked at it once and couldn't find anything out of the ordinary so I continued using it. It got worse and worse until it stopped working completely because it would not run and was partially seized.

But you did redeem yourself quite nicely!! :clap:

MrGiggles said:
On the positive side, I replaced it with a Stihl FS90R. No comparison between the two. I love it.

Just promise us if the FS90R starts knocking, you stop using it. LOL

MrGiggles · Aug 20, 2009

wigglesworth said:
Let me pioint out the first mistake.......

But you did redeem yourself quite nicely!!

Just promise us if the FS90R starts knocking, you stop using it. LOL

Yes, pretty stupid on my part I know. There's nothing I can do about it now.

Let's just hope the Stihl doesn't start knocking, ever.

MrGiggles · Aug 20, 2009

dragrcr said:
piston slap or (rock) skirts worn down and piston rocks in the bore, especially when cold as aluminum expands more that steel, so the piston will be even more loose on cold start, then run under load before warmed up. a;so usually makes a interesting egg shaped mark on the skirt

The piston was in really good shape, Nothing was worn much at all. Do you have any pics of the egg shaped mark? I know that I didn't race the engine was cold, I usually let it warm up for 30 sec before using it.