smokey7
jack of a lot ace of a few
I would agree except he said he was pretty good about maint. Like air filter and what not. It is pissible tho
Want to walk me through a piston replacement?
- Thread starter sneezer
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chuckwood
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My very first saw was a brand new Husky L65. I purchased it at a saw shop. The shop owner knew that I was a newbie so he spent a lot of time explaining maintenance to me. He showed me some broken saws he had in his shop that were plugged up with gunk and explained that saws must be kept clean inside or they will eventually overheat. I've always done that with all my saws and still have that old L65, it still runs well, all I've done is replace the rings and rebuilt the carb a couple times. I now have 2 L65's and an L77.
I don't believe that carbon caused that divot in your piston. I'm still stumped on what could have caused the plastic to melt. Was the muffler loose?
I'm thinking the fins were coated with dust/gunk and it overheated. Wouldn't be surprised. I have a 51 I bought new in 1992 and I've never had the cylinder cover off. Hard to see what all is in there. It's probably all original
smokey7
jack of a lot ace of a few
I was questioning the pattern of carbon sometimes can tell a story. I am currious of the heat issue
sneezer
ArboristSite Lurker
Lets put this one to rest about clogged fins. The answer is no. There is always some and some places where you can't easily get it out
but I have regularly looked for that and:
A) Cleaned it out occasionally and
B) There was never very much to take out
Moreover, this does not explain the melted plastic. That is very clearly adjacent to the muffler and to me it is absolutely clear
that a hot muffler melted plastic. Now the question of *why* the muffler would be so hot is another matter and though I
am not certain to be right, I did advance a potential explanation very early about raw fuel getting there and burning inside
the muffler. So far nobody has shot that one down or supported it either. Lets try to consider that. It's a possible
explanation for one area of excess heat.
Also, I now think there were two overheated areas. Not trying to be cagey but that's going to be an interesting post and
I want to get it right. But I just don't have the energy right now and will still have to rest and think about it a little.
Appreciate your patience.
but I have regularly looked for that and:
A) Cleaned it out occasionally and
B) There was never very much to take out
Moreover, this does not explain the melted plastic. That is very clearly adjacent to the muffler and to me it is absolutely clear
that a hot muffler melted plastic. Now the question of *why* the muffler would be so hot is another matter and though I
am not certain to be right, I did advance a potential explanation very early about raw fuel getting there and burning inside
the muffler. So far nobody has shot that one down or supported it either. Lets try to consider that. It's a possible
explanation for one area of excess heat.
Also, I now think there were two overheated areas. Not trying to be cagey but that's going to be an interesting post and
I want to get it right. But I just don't have the energy right now and will still have to rest and think about it a little.
Appreciate your patience.
smokey7
jack of a lot ace of a few
Ok i am taking a shot on this raw fuel deal....... how deep is the groove in the piston where it was damaged? If it is bigger/deeper then i have ever seen or the piston is undersize, you could loose your charge from the bottom end. It is possible i think.... if raw fuel vapor shot in there it sure could start a flame thrower effect right?
sneezer
ArboristSite Lurker
@smokey7
Exactly what I was thinking except you have stated it more concisely than I did.
The gouge is not very deep but I don't think it would have to be. You wouldn't
have to lose much charge. Just a tiny bit at 9000 RPM or so could cause some
really heat. Any more and it would have been really spectacular.
Consider - piston rising into power stroke, making lots of compression with a
gouge that extends downward past the top of the exhaust port. That's my
theory for the muffler heat.
Now, do we have anyone on the other side of the bench?
Exactly what I was thinking except you have stated it more concisely than I did.
The gouge is not very deep but I don't think it would have to be. You wouldn't
have to lose much charge. Just a tiny bit at 9000 RPM or so could cause some
really heat. Any more and it would have been really spectacular.
Consider - piston rising into power stroke, making lots of compression with a
gouge that extends downward past the top of the exhaust port. That's my
theory for the muffler heat.
Now, do we have anyone on the other side of the bench?
smokey7
jack of a lot ace of a few
Ok so are you thinking the flame from combustion is blowing past the gouge and into the crankcase on the up stroke? I am thinking if conditions were right fuel in a narrow stream could shoot up the groove and meet the fresh combustion gas/flame on down stroke and make a much larger heat
source. Im guessing it then went
lean from loss charge making it
unable to start. If that theory plays
out.... then what caused the
damage? Im really suspecting
bearing damage. Especially as it
sounds like you maintained it pretty
decent. Kinda sounds like it free
ported, like when you crack a skirt.
source. Im guessing it then went
lean from loss charge making it
unable to start. If that theory plays
out.... then what caused the
damage? Im really suspecting
bearing damage. Especially as it
sounds like you maintained it pretty
decent. Kinda sounds like it free
ported, like when you crack a skirt.
sneezer
ArboristSite Lurker
@smokey7
Couple pics here. First the one of the gasket that you asked for. This, to me at least looks fine
Second, the inside of the piston.
I've spent many -well, not hours- but many minutes examining this piston from every angle
and have just not been able to see it in just the way you have. The red line I added earlier
corresponds to what you were calling a "1/4 moon shaped cleaned area" or at least that's what
I thought. The green is another mark lower down and appears to be just some wear.
You mentioned carbon and there is some. The top of the piston had some but not a lot and
the combustion has some around the plug hole but again not a lot. There is quite
a bit inside the exhaust port.
OK, now to the piston pic, no. 401. There is some brown baked or cooked substance inside
there. I guess oil. The whole inside of the piston is glazed in this way but the darkest is
on the exhaust side. So that got pretty hot and this is, I think, irrefutable evidence of it.
Intake side is cooked a little but the discoloration is very slight. So, really hot on the
exhaust side. I have some thoughts on this but see that there have been a couple more
posts that I haven't read yet, so I'll stop here.
Except to ask whether we are talking chicken or egg??
Couple pics here. First the one of the gasket that you asked for. This, to me at least looks fine
Second, the inside of the piston.
I've spent many -well, not hours- but many minutes examining this piston from every angle
and have just not been able to see it in just the way you have. The red line I added earlier
corresponds to what you were calling a "1/4 moon shaped cleaned area" or at least that's what
I thought. The green is another mark lower down and appears to be just some wear.
You mentioned carbon and there is some. The top of the piston had some but not a lot and
the combustion has some around the plug hole but again not a lot. There is quite
a bit inside the exhaust port.
OK, now to the piston pic, no. 401. There is some brown baked or cooked substance inside
there. I guess oil. The whole inside of the piston is glazed in this way but the darkest is
on the exhaust side. So that got pretty hot and this is, I think, irrefutable evidence of it.
Intake side is cooked a little but the discoloration is very slight. So, really hot on the
exhaust side. I have some thoughts on this but see that there have been a couple more
posts that I haven't read yet, so I'll stop here.
Except to ask whether we are talking chicken or egg??
Attachments
sneezer
ArboristSite Lurker
Well, I'm thinking that fuel from the combustion chamber could have blown through the gouge on
upstroke and into the exhaust port. I don't see how it would get as far as the crankcase but
I think now is the time to have a look there. I do think it would go in that direction because
on upstroke that is where the pressure is. On the subsequent downstroke, some still burning
fuel could have exited and ignited the small amount of raw fuel already in the muffler. Once
ignited there it could have stayed ignited.
I don't know about it going lean. I suspect there was not enough escaping to do that but
even a tiny bit in the muffler could cause quite a blaze. I don't know much about the
going lean part but have looked at a couple of posts on the topic. I think if a lean
condition caused overheating it didn't get very far. The surfaces of both piston and
cylinder look pretty clean except the details we have talked about. And then, if it
was lean, wouldn't that heat the entire circumference of the piston and not mainly
the exhaust side. I don't see any similar signs inside the cylinder.
As far as free porting, I've only heard the word and don't know what it means.
I do have the wrist bearing out and it looks fine, almost as if new.
Not starting? Well, I didn't try very hard after seeing the rest of it so, after a bit of
cooling it might have started just finebut I thought it was not a good idea.
upstroke and into the exhaust port. I don't see how it would get as far as the crankcase but
I think now is the time to have a look there. I do think it would go in that direction because
on upstroke that is where the pressure is. On the subsequent downstroke, some still burning
fuel could have exited and ignited the small amount of raw fuel already in the muffler. Once
ignited there it could have stayed ignited.
I don't know about it going lean. I suspect there was not enough escaping to do that but
even a tiny bit in the muffler could cause quite a blaze. I don't know much about the
going lean part but have looked at a couple of posts on the topic. I think if a lean
condition caused overheating it didn't get very far. The surfaces of both piston and
cylinder look pretty clean except the details we have talked about. And then, if it
was lean, wouldn't that heat the entire circumference of the piston and not mainly
the exhaust side. I don't see any similar signs inside the cylinder.
As far as free porting, I've only heard the word and don't know what it means.
I do have the wrist bearing out and it looks fine, almost as if new.
Not starting? Well, I didn't try very hard after seeing the rest of it so, after a bit of
cooling it might have started just finebut I thought it was not a good idea.
sneezer
ArboristSite Lurker
Just took a look in the top of the crankcase. Didn't look much before because the Husky shop manual
suggests stuffing a rag in there as the cylinder is pulled off to prevent entry of a lot of crap. I
followed that advice and therefore couldn't see much until I had a chance to clean the area.
Now here's what I saw. Everything looks fine. I've never seen the inside of a crankcase before
but everything looks fine. No discoloration or marks of any kind. No pieces of anything.
The rod bearing (is that the name?) has quite a bit of side to side play (1/16") but it looks
to be designed that way. In any direction perpendicular to the axis of this bearing there is no
play that I can detect.I can turn the crank easily and smoothly. If I hold onto the wrist end
of the rod and rotate the crank fairly quickly using the rope, there is no feeling of vibration or
of anything grinding or catching or tight.
suggests stuffing a rag in there as the cylinder is pulled off to prevent entry of a lot of crap. I
followed that advice and therefore couldn't see much until I had a chance to clean the area.
Now here's what I saw. Everything looks fine. I've never seen the inside of a crankcase before
but everything looks fine. No discoloration or marks of any kind. No pieces of anything.
The rod bearing (is that the name?) has quite a bit of side to side play (1/16") but it looks
to be designed that way. In any direction perpendicular to the axis of this bearing there is no
play that I can detect.I can turn the crank easily and smoothly. If I hold onto the wrist end
of the rod and rotate the crank fairly quickly using the rope, there is no feeling of vibration or
of anything grinding or catching or tight.
smokey7
jack of a lot ace of a few
Ok we are narrowing down this chicken egg thing. Your pic of the underside of piston showes some extresm heat! I would bet if you had continued much longer you would have a melted thru spot right where the discolured spot on piston dome and underside of piston. As far as which way it happened is still up for grabs..... that piston at the edge where its chipped.... does it maybe have a crack all the way thru? Maybe fill up the piston upside down on your bench and see if it leaks thru. I am grasping a little since this is kinda unique. i really enjoy finding cause of failures.
sneezer
ArboristSite Lurker
Won't be able to post much today. Got orders from the wife to go out and watch some paint dry.
Yeah, really. She's a realtor and has a big house for sale. Clients are in Europe and it needs
some sprucing up. So guess who has to be there while the door is open.
But keep thinking. I will be back. Maybe there's a computer there anyway.
Yeah, really. She's a realtor and has a big house for sale. Clients are in Europe and it needs
some sprucing up. So guess who has to be there while the door is open.
But keep thinking. I will be back. Maybe there's a computer there anyway.
smokey7
jack of a lot ace of a few
No problem i got orders from wife too... i got to help move the inlaws. I wouldnt wish it on my worst enemy. I have never seen any other people cost me so much money. If you get a chance measure piston cyl clearance on a normal area and that that damaged spot. So i can gen a idea how deep it is.
sneezer
ArboristSite Lurker
Not sure what you mean by that measurement. I gather the intent is to discern how deep the gouge is and
therefore how it could act as a channel for escape of gases (??). I can tell you without measurement that is
no more than a couple of .001s". Yes, that has me too asking how much could get through there but
evidently it was enough.
Again, even with weaknesses in the explanation, I haven't heard any other so for now I'm sticking with
this.
@blsnelling
Muffler was not loose, I can vouch for that. This particular saw, when it was new, had a lot of trouble
with the muffler getting loose and even falling off. The two studs holding it would vibrate out of the
threaded holes in the cylinder casting and just drop out. It must have been a common problem
because before long Husqvarna changed the design of the studs and that was better. Still, they
do loosen up and I know that, so that's one thing I check pretty often.
therefore how it could act as a channel for escape of gases (??). I can tell you without measurement that is
no more than a couple of .001s". Yes, that has me too asking how much could get through there but
evidently it was enough.
Again, even with weaknesses in the explanation, I haven't heard any other so for now I'm sticking with
this.
@blsnelling
Muffler was not loose, I can vouch for that. This particular saw, when it was new, had a lot of trouble
with the muffler getting loose and even falling off. The two studs holding it would vibrate out of the
threaded holes in the cylinder casting and just drop out. It must have been a common problem
because before long Husqvarna changed the design of the studs and that was better. Still, they
do loosen up and I know that, so that's one thing I check pretty often.
