162SE scored piston

[MarkEagleUSA]

I forgot to add this saw is on it's second tank of TruFuel 50:1 since rebuilding the carb and replacing the fuel line. Prior to that it hadn't been run in almost 2 years. Everything was nice and oily in the lower end. The piston itself was really wet below the ring.

As stated earlier, I just replaced the oil pump. Either the old one or the new one likely had/have a bad seal is the best I can come up with.

 

[almondgt]

If you rebuilt the carb and didn't adjust the high low screws to accomodate 50:1 may be where your scoring issue lies.

 

[MarkEagleUSA]

If you rebuilt the carb and didn't adjust the high low screws to accomodate 50:1 may be where your scoring issue lies.

I followed all the great advice I read here... made sure she burbled out of the cut and cleaned up in. She was running fine as far as I could tell.

Then I noticed the huge oil leak a couple of weeks ago so I ordered the new AM oil pump. The old one was leaking (more like pouring out) from behind the clutch and all around the pump casing/cover. The old o-ring was shot which is why I suspect the seal may have been bad as well.

 

[SawTroll]

If you rebuilt the carb and didn't adjust the high low screws to accomodate 50:1 may be where your scoring issue lies.

Recommended mix ratio (according to the 1980 OM) was 50:1, and basic carb settings H=3/4 and L=1.

If the saw was run with more oil in the fuel earlier, 50:1 would make it run richer, not leaner.

 

[MarkEagleUSA]

basic carb settings H=3/4 and L=1

Exactly where I started after the rebuild. Again, I used the information I got from here to tune her properly.

I admit that prior to finding AS a few months ago, I probably tended to run her a little too lean most of the time. I did pop the muffler off during the carb rebuild to check the piston and it was NOT scored at that time. So I suppose it could have been the tune but I'm still going with the bad seal theory.

 

[SawTroll]

Exactly where I started after the rebuild. Again, I used the information I got from here to tune her properly.

I admit that prior to finding AS a few months ago, I probably tended to run her a little too lean most of the time. I did pop the muffler off during the carb rebuild to check the piston and it was NOT scored at that time. So I suppose it could have been the tune but I'm still going with the bad seal theory.

I suspect it was (and is) an air leak, so I tend to agree - but of course I am not there....

 

[boxygen]

So lets say this saw achieved this score through a lean tune and this was confirmed through a vac/pressure test. Is there any harm in running it as is if it runs alright which I suspect it does? Will further damage be done if it is tuned properly?

 

[discounthunter]

the top side of the piston above the ring looks like it ingested something.

 

[nmurph]

the top side of the piston above the ring looks like it ingested something.

Yep, and the very edge of the piston has cratering, typical of running poor quality fuel leading to detonation.

 

[SawTroll]

Yep, and the very edge of the piston has cratering, typical of running poor quality fuel leading to detonation.

I wasn't confident enough to post that, but it surely looks like there has been detonations - the question is when, and if it caused the scorching.....

Also, if True fuel is like Aspen, it should not be run in saws that has been run on lower quality fuel, unless all old carbon deposits are removed first.

 

[Trailtrimmer]

Yep, and the very edge of the piston has cratering, typical of running poor quality fuel leading to detonation.

Pitting and a light plug always tells me low octane or timing. Is it possible for timing to get advanced too far on that saw?

 

[nmurph]

Pitting and a light plug always tells me low octane or timing. Is it possible for timing to get advanced too far on that saw?

I should have also mentioned that it could be the carbon build up lowering the squish to the point that is it too tight.

 

[MarkEagleUSA]

the top side of the piston above the ring looks like it ingested something.

Yep, and the very edge of the piston has cratering, typical of running poor quality fuel leading to detonation.

Over the past 32 years this saw may have seen a tank or two of poor quality fuel. :redface:

Also, if True fuel is like Aspen, it should not be run in saws that has been run on lower quality fuel, unless all old carbon deposits are removed first.

So my decision to use the pre-mix was more likely the culprit here?

Pitting and a light plug always tells me low octane or timing. Is it possible for timing to get advanced too far on that saw?

I should have also mentioned that it could be the carbon build up lowering the squish to the point that is it too tight.

There was some carbon on the top of the piston, but it wasn't caked on. A little carb cleaner on a rag and most of it wiped right off.

 

[SawTroll]

....

So my decision to use the pre-mix was more likely the culprit here?

.... .

More like another remote possibility (or theory) - the scorching could have been caused by carbon flakes that got loose from the combustion chamber.

 

[MarkEagleUSA]

the top side of the piston above the ring looks like it ingested something.

When I replaced the oil pump I used one of those white plastic hook shaped piston stops when I removed the clutch (for years I used the nylon rope trick). While it wasn't evident to me, is it possible that caused a couple of pieces of carbon to dislodge and get down between the piston and cylinder? The carbon on top of the piston wasn't hard and crusty and the top part of the cylinder was more like sludge.

Also, if you look at the pics of the exhaust port you can clearly see a chunk of carbon missing on both sidewalls. Could some of that have gotten sucked back into the cylinder?

 

[nmurph]

That dimple on the right side of the pic of the exhaust port was caused by something harder than carbon. If it were my saw, I would pull the seals on both sides, flush the case and bearings with high pressure water, blow them out, and spray the bearings down with WD40, paying attention to make sure the bearings are smooth. I would reassemble it with new seals, gasket (if you insist), and a new piston. Then your saw will be good for many more years regardless of how you choose to use it. I know this sounds like a daunting challenge, but it really isn't that hard if you ask lots of questions, do lots of reading, and take your time.

 

[TK]

Edit - missed a whole page of posting

 

[MarkEagleUSA]

That dimple on the right side of the pic of the exhaust port was caused by something harder than carbon.

I might have done that during the teardown. I used a 1/4" aluminum rod with a rag wrapped around it to see if the score lines would wipe off (wishful thinking). It does look fresh...

If it were my saw, I would pull the seals on both sides, flush the case and bearings with high pressure water, blow them out, and spray the bearings down with WD40, paying attention to make sure the bearings are smooth. I would reassemble it with new seals, gasket (if you insist), and a new piston. Then your saw will be good for many more years regardless of how you choose to use it.

Leave the case together and just flush out the bearings and crankcase? Wouldn't it be wise to replace the bearing at this point?

What about the cylinder? Does it need to be honed, or can I just use some scotchbrite or fine sandpaper on it?

I know this sounds like a daunting challenge, but it really isn't that hard if you ask lots of questions, do lots of reading, and take your time.

I've done lots of reading and have rebuilt some mower engines over the years. This chainsaw will be a first for me.

 

[nmurph]

I might have done that during the teardown. I used a 1/4" aluminum rod with a rag wrapped around it to see if the score lines would wipe off (wishful thinking). It does look fresh....

The one thing that was puzzling me about the pic was the lack of scoring below that dimple. Chipping it during clutch removal would make sense.

I only remove clutches by using an impact and nothing in the cylinder. That way you are only operating against the compression of the motor. I do not use any sort of stop in the cylinder.

Leave the case together and just flush out the bearings and crankcase? Wouldn't it be wise to replace the bearing at this point?.

You can check the bearings. There should not be ANY vertical play at the crankshaft ends and they should spin smoothly. Replacing them is going to require splitting the case. It's not difficult to do if you read up and can buy/fab the tools.

What about the cylinder? Does it need to be honed, or can I just use some scotchbrite or fine sandpaper on it?.

You need to read up on using acid to remove transfer. Even a small amont left behind can render a rebuilt useless in just a few minutes.

I've done lots of reading and have rebuilt some mower engines over the years. This chainsaw will be a first for me.

Saws are easier to repair than mowers.

 

[almondgt]

Saws are easier to repair than mowers.[/QUOTE]

Saws/mowers...........parts, tools, knowledge. One is not harder than the other to repair