You're goal right now is to hopefully save the cylinder and only need a new piston.
Is running a scored saw okay if its getting the job done?
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Is that possible with compromised plating?
Replating a cyl. makes better sense when you're talking about a hi-buck Jug. Perhaps viable, economically.
Probably why a "bad" 090 jug has some value. That and perhaps the hotSaw market.
There's a diff. between 'bad' and 'totaled'.
Probably why a "bad" 090 jug has some value. That and perhaps the hotSaw market.
There's a diff. between 'bad' and 'totaled'.
Aldiehoggydoggy
ArboristSite Operative
Justsaws
Addicted to ArboristSite
Sometimes a saw will get a couple of light scratchs and nothing ever really comes about from it, sometimes a saw will get a couple of light scratchs and it fubars fast.
What saw?
What is it worth to you?
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kmcinms
ArboristSite Guru
Go big or go home, right!!! If you're gonna be a bear, be a Grizzly! :hmm3grin2orange:
First thing, check for air leaks. If it passes the test, pop the jug off that thing and clean any transferred aluminum off the cylinder. Put a piston and ring set back in it. :chainsawguy:
I guess since it is an 090 I'll change my attitude about it a little.
But, these internet forums having everybody and his brother pulling the muffler off good running saws is a little comical.
The notion that if you correct the problem that it is going to continue to get worse is not backed up by anything other than opinion.
And, my opinion from actually doing it is that if you get it tuned properly with good mix it will run just fine for a long time, probably until you are sick of it.
But, these internet forums having everybody and his brother pulling the muffler off good running saws is a little comical.
The notion that if you correct the problem that it is going to continue to get worse is not backed up by anything other than opinion.
And, my opinion from actually doing it is that if you get it tuned properly with good mix it will run just fine for a long time, probably until you are sick of it.
Nardoo
Addicted to ArboristSite
Chainsaw dealers just love fellows like you. They see dollar signs - big dollars in your case. If you have been here for seventy odd posts and you ask questions like this you just have not been paying attention. Sorry to be blunt but you are just going to ruin another 090 cylinder.
LOL. Paying attention to posts on this forum. There are plenty of guys on this forum who have no practical need for a chainsaw and have 30 or 40 of them. And, they never met a saw that didn't need to be rebuilt or ported. Sleep with them occassionally I think.
There are a zillion saws out there running every day with some scoring. And, they will still be running tomorrow provided they caught the mis-tune, bad part, or bad fuel that caused it.
Seems to me the dealers love is the guy pulling the muffler off good running saws and bringing them in for new top ends.
Threat to life and limb is imminent if you continue to use this saw, in this condition. Replace piston and cylinder immediately and send use parts to me for evaluation and disposal.
Seriously though, for your own satisfaction, what would you rather own, a saw with a worn out top end or one that has a new top end?
Seriously though, for your own satisfaction, what would you rather own, a saw with a worn out top end or one that has a new top end?
spike60
Addicted to ArboristSite
I'm amused that so many members are suggesting that you can continue to run a damaged saw with no ill effects. :msp_razz: Not sound advice IMO. There are so many pieces of equipment that fail, expensively, because their owners continued to run them while ignoring obvious signs that something was wrong. Most could be saved simply by shutting them off.
I agree that there are plenty of damaged saws being run out there, but they are on borrowed time and the more you run them, the sooner they reach the end of the line. Either the compression will gradually fall to the point where it just doesn't run, or the build up of aluminum transfer will reach a level where the piston just wipes out. At that point, it's a 50/50 chance that the cylinder will suffer some scoring that will make it unusable.
I agree that there are plenty of damaged saws being run out there, but they are on borrowed time and the more you run them, the sooner they reach the end of the line. Either the compression will gradually fall to the point where it just doesn't run, or the build up of aluminum transfer will reach a level where the piston just wipes out. At that point, it's a 50/50 chance that the cylinder will suffer some scoring that will make it unusable.
I have one question. Why do some of you insist that the aluminum transfer is going to continue to build up after the problem has been found and fixed, and it was not bad enough to seize the rings.
It comes from the piston getting so hot it melts. Once you correct that, what is causing all this new transfer?
What am I overlooking ?
Don't apologize for being blunt - it's the most efficient way to communicate. I was concerned that my post would get to this point as it seems many otherwise innocent questions incite arguments and put-downs. I could have given 100% of the backstory as well as my level of knowledge and understanding, but after too many words people stop reading anyway and the point is lost...
I'm far from being an expert, but I'm no idiot either. There is a specific reason in my initial post I said that for the sake of this inquiry I would like everyone to assume a lean condition due to a poorly adjusted H screw was the problem. Right now that's the only potential cause I've found, but I have not thoroughly tested the saw. I would never operate a damaged machine without knowing what caused the damage first. I've pulled the jug to investigate the extent of the damage and found what I expected. I ordered a new top end, but not because I'm a run-to-the-Stihl-dealer-for-new-high-margin-parts, but rather becasue I can get them at dealer cost under certain circumstances. I would never have bought this saw if I would be paying the $355 plus tax for the new top end or if all I could afford was an aftermarket replacement.
I have a complete Stihl test kit and intend to fully test & evaluate this saw before using it or making any repairs so that I fully understand what happened if it was due to a mechanical malfunction. I believe in understanding a problem before addressing it - I use far more stitches than band-aids. In my line of work we say "address the problem, not the symptom". Despite my analogies I'm not a doctor, nor do I play one on television.
I run into situations like this and my curiosity brings up questions; remember a long time ago when you had questions that you knew others would call you "stupid" for but you still wanted the answer, embarassment and belittlement aside?
Asking questions freely is a great way to learn. Assuming stupidity and lack of attention is a poor way to teach.
Excess clearance ?:msp_mellow:
Streblerm
Addicted to ArboristSite
Here's my thought. There is supposed to be minimum clearance between the cylinder and piston. Sure they are both aluminum but the cylinder with it's cooling fins and air moving over it will expand at a different rate than the piston which shouldn't be contacting the cylinder other than through the ring/s. If you have aluminum deposits on the cylinder, then that encroaches on the clearance that was designed between the piston and cylinder. As the piston expands it may contact the transfer causing friction, heat, and eventually more transfer. Its a vicious cycle.
IMO I wouldn't run a saw with known scoring. If you believe you addressed the cause of the scoring that is the first step. At a minimum I would remove the transfer, lightly sand the gouging on the piston and put in a new ring. If its a saw you care about then a new piston is in order as well.
Philip Wheelock
Finis Origine Pendet
As a general rule, is once a problem in a chainsaw, or any tool for that matter, is identified, it gets fixed before further use. In this case, catastrophic failure of the piston could result in metal making its way into the crankcase, causing further damage. Respect the tool.
Well, the way I am looking at this every saw I get for the most part is scored until it won't run. That is why they come here.
Scoring hardly ever if ever causes any damage to the bottom end. And, I have a 200T down now that has a pristine piston and the bearings are shot.
spike60
Addicted to ArboristSite
Friction maybe? Kind of causes heat?
Nah. If you get everything back in order the harder rings wear it off pretty quick. And, it goes the same place piston wear always ends up, out the exhaust.
Chris-PA
Where the Wild Things Are
The OP has stated the plating is shot above the exhaust port. Therefore, is the jug technically and/or economically salvageable or not? If not (and I suspect the answer is no) then we can leave questions about causing further damage to the jug behind, and the only issue is if running it might cause damage to the bottom end.
