Cut issue and scored piston: how much is too much?

[bbaxj]

Sorry for the novel, but I figure too much info is better than not enough. I'm sure this has all been covered before, but I figure every scenario is a little different. Scroll down if all you care about are pics.


Backstory: I'm fairly new to the chainsaw world. I bought a house with a wood burner, and started prepping to get my own firewood. I bought a used Stihl 036 about 2 years ago. It came with 3 20" bars, 1 was good, 1 junk, and 1 unknown, and a bunch of chains(all 3/8" pitch, mostly full chisel). I cut about 10 face chords with it with zero issues, then it started acting up. The first sign of a problem was it started bogging badly and running crappy. Then so did my backup saw. Pretty sure I got a batch of bad gas. I got rid of that, put new fuel in both, then both seemed fine. I replaced the fuel line around the same time just to be safe. After another 5 or so face chords the Stihl started cutting in an arc and getting pretty bogged down in anything thicker than 10" or so. Then when it was sitting on the shelf all the bar oil leaked out and made a mess. It had never had any leaks prior to that. That's pretty much where I'm at now.

First off, the cutting in an arc is worn bar and/or chain, right? I didn't know at the time that I was supposed to flip the bar periodically. I also don't know what it went through prior to my ownership.
I assumed the oil leak was a blown line or something and had caused the bar and chain to run dry and get worn out prematurely. I talked to a pretty knowledgable guy yesterday and it sounds like leaks are common and not necessarily anything to worry about. He told me to remove the bar and see if it still pumped. It did, oil flow was still very good. Then I tried a different bar and chain and had the same issue....but neither looked to be in particularly good shape either. I've got a new OEM bar and chain on the way now. Is that likely to fix the cutting issue? Are there other issues that can cause this behavior?

Second, I pulled the muffler and looked at the piston/cylinder. Now my hope is that the seemingly reduced power/bogging in the cut is just due to binding with the worn bar and chain....sound about right? So I'm really hoping with the new bar/chain it'll cut straight and feel how it did before in the power department.

So here's what I found inside the engine. I know any scoring is bad, but how much is enough to worry about? It seems pretty light compared to some I've seen online, and didn't feel very deep at all when I lightly ran a pick over it.



It might be a little worse than it looks in the pics, but not by much.
So is it junk or should I keep running it? I can handle replacing the cylinder and piston if this is shot, but I'd rather not spend the money if this one is fine.

I also did a compression test and got 150 psi repeatedly, assuming I did it right. I've never compression checked a chainsaw.

First pull would go to around 60 psi, then 90 on the second, 120, and then peak at around 150 on the fourth pull. Sound normal? I don't have a leakdown tester so I wasn't able to do that.

Thanks for any help!!

 

[Guido Salvage]

What oil and mix ratio are you running? Looks like carbon buildup on the bottom of the exhaust port. Those small chunks will get inside the cylinder and ruin it in a hurry.

 

[bbaxj]

Premium fuel with Stihl synthetic oil mixed 50:1. I'll clean the carbon out before I run it again. Any thoughts on the rest of it?

 

[nmurph]

Here's the way I see it-

You need to pull the cylinder and clean up any transfer. While you at it, and since you have gone to this trouble, why not spend the $40 and put a new piston in? Rings are going to cost you $15 and you still have scoring on the piston. As to the piston itself, yours doesn't look too bad and could probably be cleaned up with fine sandpaper and steel wool. Myself, it would get a new piston.

 

[bbaxj]

Here's the way I see it-

You need to pull the cylinder and clean up any transfer. While you at it, and since you have gone to this trouble, why not spend the $40 and put a new piston in? Rings are going to cost you $15 and you still have scoring on the piston. As to the piston itself, yours doesn't look too bad and could probably be cleaned up with fine sandpaper and steel wool. Myself, it would get a new piston.

I'm not at all opposed to doing that if it needs it.....just wanted to make sure that it does in fact need it. Should I replace the cylinder at the same time, or is that likely to still be fine with the minimal scoring I've got?

 

[nmurph]

OK...I'm at work and can see this on my big monitor. That really does look like minor damage and you might get by with just a set of rings. It looks like it may have spit a piece of carbon and that is what caused the damage. I would definitely think the cylinder can be cleaned with sandpaper and elbow grease.

 

[timberjak]

While the saw was cutting an arc was the bar oil dripping then? Dripping on the ground or boots while cutting/ operating the saw. If so the oil port/hole on bar is plugged.

The arc could just be dull chain teeth only takes a couple dull teeth.




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[Marshy]

Wow, I dont like the looks of that much carbon in the port runner. That could of been from the previous owner and no fault to your own. I would pull the muffler and try to get it out. I found that some scotch brite dipped in some sea foam makes quick work of carbon removal. I would not use and sand/emry paper or steel wool to remove it unless you have the cylinder off and can wash it down with some cleaner to get rid of the grit. Any grit left over or steel filings will destroy the piston or cylinder in quick order and once you start rubbing steel wool around on things it becomes magnitised and could stick to the ring or cylinder wall, just bad advice IMO. Since you have good compression I would not go into the top end, just run it. I've seen snomobiles make fine power with a LOT more scoring than that. I think your power issue you are having is a dull chain and nothing to do with the bar. Any time it starts cutting on a bend you have one side of the chain sharper than the other. Sounds to me like you need more practice sharpening you chain. would recommend you but a file guide with your new chain and sharpen it ever other or third tank of gas (depending if you keep it out of the dirt or not). Flipping the bar over once in a while is a good practice but not required by any means and has not effect on it cutting on a bend...

 

[redfin]

If the rail in the bar is worn to far it willl allow the drivers to lay over in the rail causing your arc. It will also create extra friction bogging the saw.

 

[nmurph]

With a compression reading of 145, he's already lost some compression and he needs remove any deposits in the cylinder. We see some relatively minor scuffing on the piston face, but we don't have a clue how the rest of the cylinder looks.

I read the OP-

A saw cutting crooked is either a bent bar, a worn rail, or unevenly filed cutters.

Oil leaking from a sitting saw isn't usually a problem. The changes in pressure as a saw warms and cools will cause it to ooze oil. There is also a vent for the oil tank and sometimes they can get stopped up and prevent the vent from equalizing pressure. A shot of carb cleaner through them will usually open them up.

 

[bbaxj]

Lots of good advice here, I appreciate all the feedback.

While the saw was cutting an arc was the bar oil dripping then? Dripping on the ground or boots while cutting/ operating the saw. If so the oil port/hole on bar is plugged.

The arc could just be dull chain teeth only takes a couple dull teeth.

I didn't notice any dripping at all. The drive teeth on the inside of the chain appear very well oiled, so I don't think that's the issue.

Wow, I dont like the looks of that much carbon in the port runner. That could of been from the previous owner and no fault to your own. I would pull the muffler and try to get it out. I found that some scotch brite dipped in some sea foam makes quick work of carbon removal. I would not use and sand/emry paper or steel wool to remove it unless you have the cylinder off and can wash it down with some cleaner to get rid of the grit. Any grit left over or steel filings will destroy the piston or cylinder in quick order and once you start rubbing steel wool around on things it becomes magnitised and could stick to the ring or cylinder wall, just bad advice IMO. Since you have good compression I would not go into the top end, just run it. I've seen snomobiles make fine power with a LOT more scoring than that. I think your power issue you are having is a dull chain and nothing to do with the bar. Any time it starts cutting on a bend you have one side of the chain sharper than the other. Sounds to me like you need more practice sharpening you chain. would recommend you but a file guide with your new chain and sharpen it ever other or third tank of gas (depending if you keep it out of the dirt or not). Flipping the bar over once in a while is a good practice but not required by any means and has not effect on it cutting on a bend...

I'll definitely get the carbon cleaned out, but I'm thinking I'll pull it all apart to do a more thorough job.
I've sharpened the chain numerous times and keep it in good cutting condition. Before buying my saw I had borrowed my dad's Stihl 025 with a fairly dull chain and hated it. Ever since then I keep mine nice and sharp.

If the rail in the bar is worn to far it willl allow the drivers to lay over in the rail causing your arc. It will also create extra friction bogging the saw.

It does seem like there's quite a bit of slop, so I'm hoping that's a big part of my issue. We'll see once the new bar and chain arrive.

With a compression reading of 145, he's already lost some compression and he needs remove any deposits in the cylinder. We see some relatively minor scuffing on the piston face, but we don't have a clue how the rest of the cylinder looks.

I read the OP-

A saw cutting crooked is either a bent bar, a worn rail, or unevenly filed cutters.

Oil leaking from a sitting saw isn't usually a problem. The changes in pressure as a saw warms and cools will cause it to ooze oil. There is also a vent for the oil tank and sometimes they can get stopped up and prevent the vent from equalizing pressure. A shot of carb cleaner through them will usually open them up.

Good info. At this point I think it's well worth my time and minimal investment to pull the cylinder, get it good and clean inside and out, and throw a new piston and rings in it. I'll get a new cylinder base gasket at the same time....not sure if this is required to be replaced every time like automotive headgaskets(I'm a car/truck guy, not an experienced chainsaw guy obviously), but for $4 I won't risk it. Guess I'll need to tune the saw a little afterward too, which will be a new experience for me.

For sharpening my chain I've been using bits like this on my Dremel: http://www.homedepot.com/p/Milescraft-7-32-in-Chain-Saw-Sharpener-Bits-2-Pack-20040715/202241676
I started off hand filing, but my buddy who's a much more experienced firewood cutter suggested those and showed me how he does it. Very easy to do. I do a lot of steel fabrication and custom grinding, so it's pretty easy for me to keep it steady and straight. I follow the angle guide mark on the teeth and take off just enough to get them nice and sharp again. I'm careful to try and keep them as even and straight as possible, but this is all just visual and by "feel". If that's a bad way to be doing it I'm open to suggestions. Is something like this worthwhile? http://www.homedepot.com/p/Blue-Max-4-200-RPM-Bench-Mount-Electric-Chainsaw-Sharpener-5655/202585719 seems like those will put a bit of an odd shaped cut on the teeth, and can't be used in the field as easily.

 

[nmurph]

I don't like the drill-mounted sharpening bits. When I tried them I tended to get too much hook on the cutter.

I wouldn't spend the money on that grinder. If you are going to buy a grinder, spend three bills and get a good one (Oregon 511A). Northern Tool also sells a grinder that will work well with some work to it. If you don't want to spend the money to buy a grinder, there are several filing guides that work well.

I prefer to grind several chains to take to the woods. Sometimes I swap them out, other times I will stop and touch the chain up with a file. I think either way works well. If you maintain your chains with a grinder, you can learn to barely kiss the cutter face with the wheel, get a good edge, and remove a minimum of metal. They are also handy for grinding back chains when have been damaged.

 

[bbaxj]

Makes sense on several chains, not sure how that didn't cross my mind considering I always bring a spare with me.

What is it about the Oregon sharpener that make it worth more than 6x the cost? At first glance it seems like they all function pretty much the same. I won't be using it nearly enough to ever wear out even the cheap ones.

 

[nmurph]

Reliability, easy to source parts, alignment, and consistency is what the extra money buys you.

 

[Guido Salvage]

You mention "slop" in the chain, that can happen with a narrower gauge chain than what the bar calls for (i.e. .050 chain in an .058 bar). The narrower gauge chain can lay over in the bar and cause the saw to cut at an angle.

 

[bbaxj]

You mention "slop" in the chain, that can happen with a narrower gauge chain than what the bar calls for (i.e. .050 chain in an .058 bar). The narrower gauge chain can lay over in the bar and cause the saw to cut at an angle.

Yep, I completely understand that. I'm pretty sure they were the right size, just worn out. It came with the saw and was in unknown condition. With any luck the new bar and chain will fix everything but the oil leak, but I'll probably throw a new piston in and give it all a good cleaning while it's on the bench. I could use a break from my Jeep project anyway, even if it's just one night.

 

[BVdog]

For a person that is kinda of new to chainsaws you are learning fast and asking great questions . I would suggest a good file guide. For the electric grinders I prefer the directional units that spin in both CW and CCW direction.

The nice thing about the file system is you won't be taking much material from the chain . I bought a nice USA made sears on eBay for $10.. Also if the cylinder needs cleaning there are some nice videos showing a great dremel method...


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[bbaxj]

I may have to pick up one of those chain guides and give it a shot. I was pretty happy with the dremel method but with the bar/chain issue I recently experienced I'm concerned I did longterm damage if they weren't even. We'll see.

Parts that are currently on the way to my house:
Hyway piston kit
Caber rings
New base and muffler gaskets
Air filter
Spark plug
Stihl 20" bar and full chisel chain

I'll give it all a good cleaning while it's apart, and attempt to give it a good tune once it goes back together. How long should I expect for break-in? If anybody feels like it, feel free to post the proper break-in procedure, otherwise I'll do some searching on here.

If all that doesn't fix it I'm buying a Husqvarna

 

[BVdog]

Don't forget to look at the Dolmar line


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[bbaxj]

Don't forget to look at the Dolmar line


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Ha I'll keep that in mind. In all reality I don't think I'll be switching away from Stihl anytime soon. I have absolutely nothing against the other brands, but I've been witness to too many good experiences with Stihl, and I'm too stubborn to just give up if this one isn't fixed with these parts....but I fully expect this to take care of it.