Want to walk me through a piston replacement?

[sneezer]

I've never done one before although it seems simple enough. Could use a little help anyway. I've
wandered through the site and found a lot of good info. Probably missed some though.

I've got a Husky 162SE built in 1981 and have had it since it was new. Have done some small
parts replacement over the years but this one is a surprise and a bigger challenge.

I like the saw and want to keep it. At my age (75) I really don't want a new one. Besides, with
a little TLC this one could go into my estate in, say, another 25 years.

The saw has run fine until a few days ago, then it began to balk if I had to stop and restart.
Got it running one time and it blew out a high-velocity stream of light gray smoke. Should
have stopped then but didn't. I made a cut through a 20" red oak and all seemed fine. No
apparent loss of power. Afterwards I noticed the top-end housing was melted next to the
muffler and then the saw wouldn't start. I took off the muffler and looked inside. There
appeared to be a flaw in the top rim of the piston and a streak of oil below it. By the way,
everything still moved smoothly and no sign of seizing up. Took the muffler off and looked
inside where there appeared to be some kind of flaw in the top rim of the piston, inside
the exhaust port. So, I pulled the cylinder to see more and found that a small chip, about
1/8" wide had been taken out of the lip of the piston with a gouge about 3/4" long
below it (probably the stroke length). Inside the cylinder, everything is smooth with,
at most a few streaks of discoloration, except that in the top edge of the exhaust port there
is a tiny dimple. I can see it only by some light off it and can barely find it with a fingernail.
Everything else looks and feels bright and smooth.

So, now I'm wondering what I need. I guess a piston for certain but what about the cylinder.
That mark is so small I wonder if I couldn't just burnish it a little.

I can find parts. A used cylinder and piston for $80 plus maybe a new bearing and gasket.
Or a new piston at about $25 plus shipping from Europe.

First job - get the old piston off and I'm not sure about that. I can see the hooks in the two
circlips, so I guess those will just pull out. Then drive out the wristpin? Is that it? I don't
have a drift that size, so is it crucial to buy something or can I improvise with a bit of rod
or even wood?

Well, anybody want to help an old geezer? I'm not going to write more just now because
I've just about told the story and I'm sure to have plenty of questions later.

Thanks, all.

 

[pioneerguy600]

The wrist pin will just push out, no drifting required. Take both circlips out and just find something that will fit the inside diameter of the pin, I use a taper punch that is a lesser diameter than the pin itself, its about 8 - 9 mm dia. The pin should push out easily unless there is some build up under the piston dome, a little WD40 or other solvent/penetrate and some twisting/rolling of the pin will help remove it.

 

[sneezer]

@pioneerguy600
Thanks for that.
Just found out where our cameras are so I'll try to get some pics.
Might get a better idea that way what needs to be replaced and what I can keep.

 

[sneezer]

Ok, it's out. You were right, no drifting. Just a little shove with a popsicle stick.

Here are some pics of the piston. You can see the spot where the chip came out
and the resulting gouge. I guess this one's shot but my question now is the
cylinder. I don't have a pic of this yet and may not be able to get one as the
nick in the top edge of the exhaust port may be too hard to see unless I can
get some light in there.

I'm wondering though if such a small nick in the top edge of the exhaust
port would make much difference. I'm not a perfectionist; I just want it to
work and after all if you can "port" these cylinders, wouldn't that amount
to the same thing?

Any opinions or comments on my ignorance?

 

[smokey7]

I would really like to see the jug pics. I have used some rough pistons and cylinders. So far i have only had one failure after the first failure. That was from the plating just flaking off from poor plating. The first failure exposed the bad plating spot. Did you do a compression check or pressure/vac test before it was pulled down? Aside from the damage spot that piston looks beautiful. I am very curious as to what caused the heat to melt stuff. That.piston sure does not show high heat to me. Here is a pic of a jug after a crank bearing failure. Cleaned up the gouges and its still running, its not stock either running high comp and muff mod.

 

[whitedogone]

Jug.......not so good.

 

[smokey7]

Mine you speek ove? It was not ideal but runs well...

 

[sneezer]

@smokey7
Thought you'd never ask (or anyone). About the heat, that is. No, actually, I've been thinking pretty hard about what would do this
and didn't really want to shoot my mouth off until someone else had a try or showed some interest. Here's two pics of the cover.
I've cleaned off all the grunge so what you see is all heat damage. And, by the way, the only heat damage I see (so far) is to
the plastic cover.

Now I do have a theory. I'm thinking that this little chip and gouge somehow allowed a bit of fresh fuel and air to be ejected
straight into the exhaust and that it then burned inside the muffler. Anyone else got a better idea?

The thing I haven't been able to figure out is where this fuel came from - crankcase or top cylinder? and does it even matter?
Now that I think of it though, here is what I said in my first post, " it blew out a high-velocity stream of light gray smoke".
A more detailed description of that is that it looked almost like an 18" steel rod sticking out the front of the muffler, except
that it was translucent. Weird description, eh? But that's what it looked like. Sorry, I don't have a pic and will never get one.
But now that I think of it, that exhaust would have had to be under some pressure to do that. So, likely top cylinder.
Anyone follow me, or maybe going in a different direction?

So the question I now ask is if I re-use the cylinder with a small nick in the upper edge of the exhaust port, will it do the
same thing?

I know I need to get a photo of that nick but maybe not today. It's more than a few minutes because I have to figure
out how to get enough light down in there that you can even see the nick. Unfortunately, the wife is coming back today
after 10 days in CA with the grandkids and I have to spend all day to make pretty. Hide my junk, sweep the floor, wash
the dishes, etc. etc. and then explain why I didn't get rid of that big log out by the end of the driveway. It's not that
often that I get the chance to spend a few days fooling with chainsaws and listening to French music, so I confess,I did
kick back a bit and now have to pay the piper. So a cylinder pic might take a while.

No, I didn't do any compression check or pressure/vac test. I don't have the tools for those things. However, on the last cut
I made, the saw was running fine and did not lose any power. After the cut it didn't stop until I turned it off.

Thanks, all, for your help. Looks like it might turn out OK and this saw may go into my estate after all. But who would
want it by then?

 

[smokey7]

That is quite a post. Ok so i dont believe that if the chip nick is that small that could cause this. it sure looks like something went thru that top end. How does the lower nod bearing look? Do you have and up and down play. Side to side is normal. The picture i showed you is from a lower rod bearing failure. As far as the damage assuming the bearings are good and air filter was installed, is anything else running the same fuel? I am thinking of detonation.... is your spark plug missing the ground electrode? I had a terrible batch of fuel with tons of ethanol and my leaf blower got so hot it started melting the plastic around the muffler. If you look closely at p&c do you see any little craters dimples or dents anywhere on the combustion surfaces?

 

[blsnelling]

There was most definitely a foreign object in that saw.

 

[pioneerguy600]

Ok, it's out. You were right, no drifting. Just a little shove with a popsicle stick.

Here are some pics of the piston. You can see the spot where the chip came out
and the resulting gouge. I guess this one's shot but my question now is the
cylinder. I don't have a pic of this yet and may not be able to get one as the
nick in the top edge of the exhaust port may be too hard to see unless I can
get some light in there.

I'm wondering though if such a small nick in the top edge of the exhaust
port would make much difference. I'm not a perfectionist; I just want it to
work and after all if you can "port" these cylinders, wouldn't that amount
to the same thing?

Any opinions or comments on my ignorance?

If you can file the dent down so that it is not projecting out into the cylinder bore, so that the piston rings won`t catch it then you could run that jug, I would on my own saws. If the dent is as small as you say that would be easy to lower and it won`t hurt compression enough to worry about, you should see some of the stuff I have fixed up and its still running 10 -15 years down the road.

 

[sneezer]

Well, maybe (or definitely if you will) a foreign object. I wouldn't argue it but my problem now is what to do about it.
smokey7 seems to be saying to look at everything before putting it back together and I tend to agree with that.
However, I consistently use (and clean) the air cleaner. Everything else looks firm and clean with no extra play
but I could have another look. The fuel is used in another saw and a couple of trimmers, none of which have had
problems. It is E-zero (no ethanol) 91 octane and I use a high quality 2 cycle oil, usually Stihl synthetic.
No craters dimples or dents anywhere inside that I can see. Everything is shiny and slippery to the touch of a
finger except the chip and gouge in the piston and the tiny nick at the exhaust port.

@smokey7 "Ok so i dont believe that if the chip nick is that small that could cause this."

The nick in the cylinder is tiny. The chip out of the piston is bigger as you have seen. A new piston would
not be chipped like this one and I do lean in your direction in thinking that just that little nick that is
left might not cause any trouble but I just don't know. That's why I'm here.

 

[sneezer]

Sorry about the last post. I wrote it and then forgot to upload it. Too busy with the sweeping,
I guess.

@pioneerguy600
Sounds encouraging and I wouldn't even have to file very much, if any.
Probably should touch it with something though and I'd still like to get
a pic loaded.

 

[blsnelling]

If that "tiny nick" is raised at all, you will have problems. The high spot must be knocked down.

 

[sneezer]

Incidentally, I just took a look at the two existing rings and neither one is marred or
even scratched in the slightest. These had to pass over the area many thousands of
times, didn't they? So if anything were raised there, it would have already caused
trouble with these, no?

 

[chuckwood]

There was most definitely a foreign object in that saw.

I had something like that happen to my L65 shortly after I took the carb completely apart and rebuilt it. I'd not tightened a screw enough on the choke butterfly, and it eventually came loose, got sucked into the top end, and trashed everything before it got spat out. I think I'll use thread locker on any more screws reinstalled in carburetor bores. This guy's cylinder looks ok to me, that should buff out just fine.

 

[BigDee]

Incidentally, I just took a look at the two existing rings and neither one is marred oreven scratched in the slightest. These had to pass over the area many thousands of
times, didn't they? So if anything were raised there, it would have already caused
trouble with these, no?

Yes the rings should show something.

Did I miss something or was it already discussed that the piston damage came before those rings were installed? If it ran ok before I would transpose the rings, clean up everything rough in the cylinder, and put it together. Then check the air filter and the high speed jet and evaluate again from there. How was the plug?

 

[pioneerguy600]

Incidentally, I just took a look at the two existing rings and neither one is marred or
even scratched in the slightest. These had to pass over the area many thousands of
times, didn't they? So if anything were raised there, it would have already caused
trouble with these, no?

If there was a raised spot in the cylinder wall then there would be corresponding marks on the rings and the rings would have marked/ rubbed that high spot hard, possibly wearing the plating through.

 

[blsnelling]

Sounds like you might be good to go.

 

[pioneerguy600]

I had something like that happen to my L65 shortly after I took the carb completely apart and rebuilt it. I'd not tightened a screw enough on the choke butterfly, and it eventually came loose, got sucked into the top end, and trashed everything before it got spat out. I think I'll use thread locker on any more screws reinstalled in carburetor bores. This guy's cylinder looks ok to me, that should buff out just fine.

The screws on choke and throttle butterflys need to be expanded on the extending threaded end to prevent them from backing out.