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Author Topic: Piston damage from leaning on a saw too hard?  (Read 2439 times)

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Offline LeeB

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Piston damage from leaning on a saw too hard?
« on: May 22, 2014, 11:36:47 pm »
You need to be careful leaning too hard.  When you reef on the saw, you push the piston into the thrust side of the cylinder.  The only thing that separates the two is a thin film of oil.  Pull the muffler and take a look.  If the piston is scored to the point of loosing compression, you will need to clean it up/replace it

Saw this quote in another thread . Anybody have any insights on this? Where on the piston would the damage show up? Would it only be on one side? Which side? Could it cause the ring to sieze?

'98 LT40HDD/Lombardini, Case 580L, Cat D4C, Ford 851 tractor, JD 3032 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton and 2005 1 ton Dodge 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Offline CTYank

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Re: Piston damage from leaning on a saw too hard?
« Reply #1 on: May 23, 2014, 03:53:18 am »
You need to be careful leaning too hard.  When you reef on the saw, you push the piston into the thrust side of the cylinder.  The only thing that separates the two is a thin film of oil.  Pull the muffler and take a look.  If the piston is scored to the point of loosing compression, you will need to clean it up/replace it

Saw this quote in another thread . Anybody have any insights on this? Where on the piston would the damage show up? Would it only be on one side? Which side? Could it cause the ring to sieze?

IMHO, not true. If you're feeding the engine a suitable mix of fuel:oil, mixed with proper amount of air at the carb, as you load it down excessively, you might damage the clutch from slipping. Not the piston. Prime suspect for piston damage generally will be excessive leanness, like from carb adjustment, fuel line probs, or air leaks. Overheating will do the damage, and associated reduction of oil delivery will speed it up.

If you're driven to load a saw to that extent, maybe you should shift your focus to sharpening the chain.
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Offline LeeB

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Re: Piston damage from leaning on a saw too hard?
« Reply #2 on: May 23, 2014, 04:14:16 am »
Well now, I'm not driven to loading a saw any more than it takes to let it self feed and know full well that it takes a sharp chain to be able to do that. Unfortunately, the fella my wife hired to do some handywork around the house and decided it would be ok to let him use my saw is not that educated in how to properly use a saw. I now have a trashed saw that I will replace P&C on when I get home again. When I tore it down, I did notice that the bar and chain were a bit abused. Based on what I had read in the other thread, I wondered if he may have gotten a bit heavy handed and overheated the saw, causing the problems. I do plan on replacing fuel lines and impulse line also. Just want to make sure I know what happened to start with so I don't have to do it all over again. This saw had very little hours on it.
Thank you very much for your insight.
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, Ford 851 tractor, JD 3032 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton and 2005 1 ton Dodge 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Offline Andyshine77

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Re: Piston damage from leaning on a saw too hard?
« Reply #3 on: May 23, 2014, 05:07:23 am »
Overloading and running a dull chain, can most certainly overheat a saw with a normal tuning. Saws don't handle contentious running under heavy load very well. Most guys that run a saw on a mill, tune the saw excessively rich, run more oil and let the saw idle to cool down every now and then. I've repaired quite a few saws that were ran hard with dull chains.   
Andre.

Offline LeeB

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Re: Piston damage from leaning on a saw too hard?
« Reply #4 on: May 23, 2014, 05:31:32 am »
Andy, did the damage look the same as a leaned out saw? Was it predominately on the exhaust side?
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, Ford 851 tractor, JD 3032 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton and 2005 1 ton Dodge 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Offline Al_Smith

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Re: Piston damage from leaning on a saw too hard?
« Reply #5 on: May 23, 2014, 07:07:04 am »
For that matter a saw can cook itself from its' own restricted muffler .

Case in point being an 024 Stihl I got from a dealer .As it goes that model as well as its' cousin the 026 had three different muffler systems .It turned out the most restrictive was on that praticular saw .

All I did was cut the baffle cage out ,enlarge the outlet hole and ran the thing like I stole it .Three years later in spite of a slightly cooked exhaust side piston it's never failed me yet .

Of course true to form I did and have used good old 32 to 1 fuel mixture just so I had some fodder to fling in the oil wars  8)

Offline LeeB

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Re: Piston damage from leaning on a saw too hard?
« Reply #6 on: May 23, 2014, 08:11:39 am »
How long would it take a lean saw to cook itself? I know I'm asking a lot of questions, but ireally want to learn so I don't end up with another fried saw. Would a half deaf person like myself be able to hear the difference if a saw was to start running lean? I'm still wanting to believe that the boy just overworked the poor thing, judging by the chain and bar condition.
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, Ford 851 tractor, JD 3032 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton and 2005 1 ton Dodge 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Online Ianab

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Re: Piston damage from leaning on a saw too hard?
« Reply #7 on: May 23, 2014, 08:29:00 am »
If a saw starts running lean you hear the difference. Like when it's running out of gas. It revs high, but has no power. At that point you hit the kill switch and go and fuel it up. If you don't it stops a couple seconds later anyway. So no damage.

Now if you have a blocked up carb jet or an air leak, it does a similar thing.  If you shut it down and work out what's wrong, then no serious damage.  But if you decide to finish the cut, you can toast the saw in way less than a minute.

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Offline LeeB

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Re: Piston damage from leaning on a saw too hard?
« Reply #8 on: May 23, 2014, 08:36:52 am »
Unfortunately I was not there to hear what happened. The hired hand swears it did not rev up and died in the middle of a cut.








'98 LT40HDD/Lombardini, Case 580L, Cat D4C, Ford 851 tractor, JD 3032 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton and 2005 1 ton Dodge 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Offline old guy

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Re: Piston damage from leaning on a saw too hard?
« Reply #9 on: May 23, 2014, 10:29:03 am »
I was recently given a stihl saw with the p&c scored at the exhaust port, there were 6 chains with the saw, carlton, oregon and stihl chains and I think the chains tell the story, they are badly streched and loose and I can see movement in the rivets yet for the most part the cutters are still near their full length and very dull, I think this saw was worked to death with dull chain.

  John

Offline jargo432

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Re: Piston damage from leaning on a saw too hard?
« Reply #10 on: May 23, 2014, 02:02:48 pm »
Did the hired hand use his own fuel?  I'd venture to guess he put regular gas in it.

Did your wife tell you how long it was going to be before SHE buys you a new saw?  ;D
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Offline LeeB

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Re: Piston damage from leaning on a saw too hard?
« Reply #11 on: May 23, 2014, 02:08:11 pm »
He used gas that I mixed and have since run a couple of tanks full in other saws and the weedeater. Not the gas. I already bought two more saws and parts to repair this one.  ;D
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, Ford 851 tractor, JD 3032 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton and 2005 1 ton Dodge 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Offline ehp

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Re: Piston damage from leaning on a saw too hard?
« Reply #12 on: May 23, 2014, 06:47:05 pm »
OK I see this alot , I get at least 10 or so farmers a year wanting to know why their 660 stihl blew up as I live in pretty much Stihl country , You get the same story 99.9% of the time , I was running it with the 20 inch bar on it and had a big tree to fall and cut up so put the 36 inch setup on it , They never richen the saw up to handle the longer bar and alot longer cuts so it lean burned from to much heat . If you push to hard or dull the chain out to bad and keep cutting you raise the heat temp. in the motor , the hotter the motor the leaner it becomes until its all over but the crying

Offline CTYank

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Re: Piston damage from leaning on a saw too hard?
« Reply #13 on: May 24, 2014, 07:19:59 am »
If you want do roast p&c, run a saw hard & lean & long.

Betcha the kid grabbed a fuel jug with no mix oil. Kids will do that. Lets the smoke out. Of course he won't tell.

Proper mix and air:fuel ratio, he'd torture the b&c, and himself.

If it's being fed properly, no need to "richen things up".
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Offline LeeB

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Re: Piston damage from leaning on a saw too hard?
« Reply #14 on: May 24, 2014, 07:42:41 am »
Actually 'boy' was a bad choice of words. He's as old as I am. Fuel mix was good, mixed it myself and have run a few tank fulls through 2 other saws and a weedeater. He did torture the bar and chain. 16" .050 bar, .325 chain. Mid range of the recomended size by Husqvarna. 
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, Ford 851 tractor, JD 3032 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton and 2005 1 ton Dodge 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Offline bandmiller2

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Re: Piston damage from leaning on a saw too hard?
« Reply #15 on: May 24, 2014, 08:26:32 am »
Too much heat is the killer of saws, it comes from dull chains, blocked coolant air passages and leaning on the saw to cut. Anything that reduces the RPM from normal is lugging. Back in the gear drive days you could get away with leaning on it, but not with the high rev wonders. Frank C.
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Offline Andyshine77

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Re: Piston damage from leaning on a saw too hard?
« Reply #16 on: May 24, 2014, 08:47:17 am »
Too much heat is the killer of saws, it comes from dull chains, blocked coolant air passages and leaning on the saw to cut. Anything that reduces the RPM from normal is lugging. Back in the gear drive days you could get away with leaning on it, but not with the high rev wonders. Frank C.

Correct!!!

I just don't get how some people think 10 minus to cut through a twig is perfectly acceptable, or normal.
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Re: Piston damage from leaning on a saw too hard?
« Reply #17 on: May 25, 2014, 12:22:23 pm »
LeeB, pop the clutch off and look for excessive accumulated crap.  It may be that the drive side seal leaks when the saw is cutting horizontally.  Leaking seal = lean mix = dead saw in seconds.  It could be the other side but the drive side seems to go first.
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Offline LeeB

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Re: Piston damage from leaning on a saw too hard?
« Reply #18 on: May 25, 2014, 01:27:29 pm »
It has an outboard clutch. I didn't notice a bunch of crud around the sprocket, But I will certainly have a look when I get home. I'll be rebuilding it this time while I'm off.
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, Ford 851 tractor, JD 3032 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton and 2005 1 ton Dodge 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Offline sharkey

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Re: Piston damage from leaning on a saw too hard?
« Reply #19 on: May 25, 2014, 05:21:57 pm »
That was my statement and I stand by it.  A two stroke engine has a thrust side to the cylinder, which is the exhaust side.  Why when a two stroke engine over heats is it always scored on the exhaust side?  Some of you need to go back to school... 

Offline Hilltop366

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Re: Piston damage from leaning on a saw too hard?
« Reply #20 on: May 25, 2014, 07:51:56 pm »
That was my statement and I stand by it.  A two stroke engine has a thrust side to the cylinder, which is the exhaust side.  Why when a two stroke engine over heats is it always scored on the exhaust side?  Some of you need to go back to school... 

Can't argue your point but I always figured it had a lot to do with the cool fuel with lube on the carb side as well as the cooling from the venturi effect of the carb verses hot spent gases on the muffler side along with the hot muffler.


Offline Al_Smith

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Re: Piston damage from leaning on a saw too hard?
« Reply #21 on: May 26, 2014, 03:59:28 am »
 :D Well it's simple enough to determine the reason a two cycle engine scorchs the exhaust side is because that's the side that gets hot .

Lean fuel mixtures burn faster which also means hotter .Shucks you can burn up valves and holes in the pistons of a 4 cycle for that matter from a lean mixture or air leak .

Offline CTYank

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Re: Piston damage from leaning on a saw too hard?
« Reply #22 on: May 30, 2014, 03:11:19 am »
:D Well it's simple enough to determine the reason a two cycle engine scorchs the exhaust side is because that's the side that gets hot .

Lean fuel mixtures burn faster which also means hotter .Shucks you can burn up valves and holes in the pistons of a 4 cycle for that matter from a lean mixture or air leak .

I think you hit on it. It's likely IMHO that the remaining culprit is excessively lean high-speed mixture. And the OP hasn't yet said how he regularly? cleans the engine fins. Those two will heat things up.

The piston side-thrust thing is a "red herring". It's imbalance of heat-in to heat-out. During compression, piston thrust will be against intake side, y'know!

Back when, when I was still young and foolish, and daylight was running out while cutting up some big sticks, I'd on occasion just dig in with the "spurs" to get it done. Got a little bar discoloration at times, but big Poulan took it in stride. Manual oiling on top of automatic probably helped a bit.
'72 blue Homelite 150
Echo 315, SRM-200DA
Poulan 2400, PP5020, PP4218
RedMax GZ4000, "Mac" 35 cc, Dolmar PS-6100
Husqy 576XP-AT
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Mix of mauls
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Offline LeeB

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Re: Piston damage from leaning on a saw too hard?
« Reply #23 on: May 30, 2014, 07:44:17 am »
CTY, You seem to have it in your head that OP was the one that fried his saw, and doesn't take care of it at all. OP would like for you to know that he cleans his saws regularly, keeps a sharp chain, and uses a proper sized saw for the job. OP's saw was trashed by another user when OP wasn't home, making OP quite unhappy with OP's wife for letting someone else use it. Last night the wife did tell me that while the hired help was using the saw it did rev up just before dying. First time anyone had told me this. So yes, it does now sound as if it scorched due to an air leak. 
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, Ford 851 tractor, JD 3032 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton and 2005 1 ton Dodge 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Offline CTYank

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Re: Piston damage from leaning on a saw too hard?
« Reply #24 on: June 01, 2014, 11:42:52 pm »
CTY, You seem to have it in your head that OP was the one that fried his saw, and doesn't take care of it at all. OP would like for you to know that he cleans his saws regularly, keeps a sharp chain, and uses a proper sized saw for the job. OP's saw was trashed by another user when OP wasn't home, making OP quite unhappy with OP's wife for letting someone else use it. Last night the wife did tell me that while the hired help was using the saw it did rev up just before dying. First time anyone had told me this. So yes, it does now sound as if it scorched due to an air leak.

Don't get all haired-up just because it appears that really important things may have been overlooked, and some of us are trying to find out the facts. Please don't exaggerate so wildly. Relax and let investigation go where the facts or their absence lead. It's difficult enough to try to help blind.

What I "have in my head" in fact you don't have a clue to, so can the judgment, and mis-quoting. End of story.
'72 blue Homelite 150
Echo 315, SRM-200DA
Poulan 2400, PP5020, PP4218
RedMax GZ4000, "Mac" 35 cc, Dolmar PS-6100
Husqy 576XP-AT
Tanaka 260 PF Polesaw, TBC-270PFD, ECS-3351B
Mix of mauls
Morso 7110

Offline LeeB

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Re: Piston damage from leaning on a saw too hard?
« Reply #25 on: June 02, 2014, 01:10:34 am »
If you want to help then I welcome that, but I have to say that your delivery leaves me a little confounded. Try asking me what I have or have not done to the saw rather than just wondering if OP has cleaned the fins or not.
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, Ford 851 tractor, JD 3032 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton and 2005 1 ton Dodge 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.