spike60
Addicted to ArboristSite
You've absolutely got to be kidding.
The idea that a partially damaged saw will heal itself by continued running is hilarious.
Is running a scored saw okay if its getting the job done?
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You've absolutely got to be kidding.
The idea that a partially damaged saw will heal itself by continued running is hilarious.
You've absolutely got to be kidding.
The idea that a partially damaged saw will heal itself by continued running is hilarious.
Not saying it will heal itself. But, this notion that a little scoring has ruined a saw from having any useful life left unless you rebuild it is forum BS.
Thank you for reading carefully! The jug does have plating missing just above the exhaust port so I do not consider it salvageable. It's actually intriguing to me how little scoring/transfer there is and then a large chunk of plating went to the wind! If not for the plating issue I would not hesitate to reuse the jug.
I am not/was not concerned about further damage to the piston or cylinder. I was only curious how realistic damage outside of those components was with continued use. Not just for this particular saw either, it is essentially just something I'd been wondering about for some time and it popped up again with this saw. Not the first time I've had an otherwise good running saw that told a different story when dissected.
Chris-PA
Where the Wild Things Are
At the other end of the saw spectrum, I had a 42cc Craftsman/Poulan with a Nikasil cylinder that had gotten scored. I did not know it and ran the saw for years. After joining AS and looking more closely at it I found the scoring. There were three distinct stripes in the cylinder, and a corresponding tab worn in each spot on the ring. The scores were deep, maybe 0.12" to 0.015", with the widest being maybe 0.050" wide. It blew over 130psi and ran great. I did replace the engine but I could have run it that way for much longer and it is unlikely it would have done damage to the bottom end. Different animal and different situation for sure.
Justsaws
Addicted to ArboristSite
Experience. Depends on a lot of variables but in general once it starts it does not stop. Same with the missing plating, once it starts it does not stop, correcting the carb setting will not fix that. Sometimes a saw will last quite a while with scored P/C, certainly last longer if it was a reed breather.
My opinion is that the saw in question has be run with a crappy air filter and worn out carb kit for quite a while. It has some P/C damage, and probably some crap in the crankcase. Is running it with a damaged P/C a good idea, probably not? It is however only a 090 so no big deal, besides installing a new top end on an 090 without doing a complete tear down is basically wasting money unless it is getting flipped to become a shelf holder, which almost all are so....
spike60
Addicted to ArboristSite
OK on that I agree. We're probably not that far apart and maybe thinking in terms of different amounts of scoring.
A "little scoring" would not prevent a saw from having a fair amount of useful life left. Might not be at peak compression/power, but it doesn't really need to be. It might run for a while that way, but in most cases compression will continue to drop til it becomes something serious.
The saw in question is all original and has so little use on it you can only see marks on the drive sprocket if you catch it in the right light. 99% of the paint is still on the bar and the chain still has the factory grind. For this reason I see no value in a complete tear down/rebuild. It will be thoroughly tested & evaluated and if I find any issues further repairs/replacements will be made for that reason only.
I didn't ask what caused the damage. I didn't ask what work I should do or how I should spend ("waste") my money. I was very interested in opinions and experiences from from AS members on the realistic consequences of operating a saw if the only reason you know it's scored is from looking . . . not from performance losses.
Bingo
ArboristSite Operative
090 scored p/c
If I had your 090 and I had already ordered a new top end (p/c), I'd just install it and get that nice saw up and running correctly. At that point you can sell it w/the buyer knowing he's getting a good saw w/a new top end or you can then just use it for a long time. After that I might play w/the cyl and see how it comes out...maybe put some pics up here for the builders to study and comment on. If the cyl is salvagable at all someone will want it. But at that point you are past the repair and are only offering up fodder for this forum. Sounds like you are committed to fixing the saw correctly so you might as well. You've gotten good advice...you just have to sort it out.
If I had your 090 and I had already ordered a new top end (p/c), I'd just install it and get that nice saw up and running correctly. At that point you can sell it w/the buyer knowing he's getting a good saw w/a new top end or you can then just use it for a long time. After that I might play w/the cyl and see how it comes out...maybe put some pics up here for the builders to study and comment on. If the cyl is salvagable at all someone will want it. But at that point you are past the repair and are only offering up fodder for this forum. Sounds like you are committed to fixing the saw correctly so you might as well. You've gotten good advice...you just have to sort it out.
Yeah, if I had known it was an 090 to start with I would have made a little different suggestion. But, I have done a lot of work for poor people in the community who could not pay for a proper repair. I never charge them labor and have been known not to even charge for the parts. Often the complaint will be that the saw won't cut, lost power, or however they explain it. Typically it was leaning out from one of the usual suspects but they caught it before the rings seized. Light scoring is pretty common. I do whatever is they cheapest thing to get them back going, usually just trying to keep warm. I have been amazed how well and how long some really rough looking P&C's would keep going.
Just an humble question, and not meant to antagonize in any way.
Do you sell on eBaY?
Sure I do. And, I explain exactly what the deal is. Some are like new stock, some dogs, some rebuilt, whatever. Have 100% feedback and give 14 days money back no questions asked.
Justsaws
Addicted to ArboristSite
Light scoring can be seen straight out of the box sometimes. It all about perspective, and expectations in my opinion. I have lots of saws that the piston is "repaired" and the cylinder has been cleaned up on, they work. I often prefer doing that to using aftermarket P/C sets. I almost never run a cylinder with missing plating, especially on expensive saws, lesson learned.
For me the deal about damage to the lower end is mostly about heat and abrassive materials. Not all the plating is going out the exhaust and light scoring and missing plating could be two seperate issues or one could have caused the other, in any event the longer the cylinder is used the more of it that will end up in the crankcase. Would I be super concerned about a Stihl 660, no not really. A bit more concerned on an 090, yes, especially if I was getting ready to bolt a hopefully at cost OEM 090 top end on a saw that previously had both missing plating and light scoring.
At the end of the day, not my saw, not my money.
Last edited:
laddo90
ArboristSite Operative
really
Update on the 090
This thread originally went in a different direction than I wanted it to as I was just trying to satisfy a curiosity. Regardless of why it went where it went I figured I would throw out an update on what's going on with the project...
See the photo below showing the piston on the exhaust side. I didn't take any photos when I had the jug off, but described the condition earlier in the thread. The piston rings still move and the saw currently makes right around 150 psi compression. I have pressure & vacuum tested the crankcase at 0.5 bar per the manual with zero leakage. I pressure tested the carb at 0.4 bar per the manual with zero leakage. I tested the fuel system as well and verified that the pickup and tank vent are functioning well and there are no leaks in the fuel lines.
View attachment 283385
To the best of my abilities It's been completely gone over and tuned so it starts, revs, idles, runs, and oils well. I now plan to do some cutting with it, but probably not much. I wish I'd photographed the piston and cylinder wall when I had it apart, but that's just the way the cookie crumbles. I'm planning to run it with a safe 30:1 mix using non-ethenol gas and Stihl HP Ultra oil. After I use it in the current condition I'll be doing a thorough rebuild of the top end and peripherals. I've ordered the following new OEM components:
- cylinder & piston assembly
- cylinder base gasket
- exhaust gasket
- all (4) carb/intake gaskets
- carb spacer flange
- washers & nuts for carb/intake
It has exceedingly little time on it. That, combined with a successful evaluation is reason enough to keep all of the original bearings I believe. Due to complete success on the pressure/vacuum tests I don't plan to mess with the seals either since I won't be disrupting them for a top end rebuild. There are no oil or fuel mix leaks anywhere, so I see no value in replacing any of the body gaskets. I think any job doing is worth doing right, but I don't believe in replacing parts 'just because'. Since I don't see any value in replacing the bearings or seals I don't plan to do so. I know some folks disagree with this, but since it has completely tested out I think it's a solid decision. Also, I will obviously be thoroughly testing it post-rebuild as well.
It's quite an impressive machine and I'm excited to cut with it! I wrote this to share my experience, but based on what I've seen so far in the forum there is a good potential for criticism and heated discussion. I do welcome any sound advice or suggestions though realted to my game plan. I'm always interested in learning and want to do this project the right way.
This thread originally went in a different direction than I wanted it to as I was just trying to satisfy a curiosity. Regardless of why it went where it went I figured I would throw out an update on what's going on with the project...
See the photo below showing the piston on the exhaust side. I didn't take any photos when I had the jug off, but described the condition earlier in the thread. The piston rings still move and the saw currently makes right around 150 psi compression. I have pressure & vacuum tested the crankcase at 0.5 bar per the manual with zero leakage. I pressure tested the carb at 0.4 bar per the manual with zero leakage. I tested the fuel system as well and verified that the pickup and tank vent are functioning well and there are no leaks in the fuel lines.
View attachment 283385
To the best of my abilities It's been completely gone over and tuned so it starts, revs, idles, runs, and oils well. I now plan to do some cutting with it, but probably not much. I wish I'd photographed the piston and cylinder wall when I had it apart, but that's just the way the cookie crumbles. I'm planning to run it with a safe 30:1 mix using non-ethenol gas and Stihl HP Ultra oil. After I use it in the current condition I'll be doing a thorough rebuild of the top end and peripherals. I've ordered the following new OEM components:
- cylinder & piston assembly
- cylinder base gasket
- exhaust gasket
- all (4) carb/intake gaskets
- carb spacer flange
- washers & nuts for carb/intake
It has exceedingly little time on it. That, combined with a successful evaluation is reason enough to keep all of the original bearings I believe. Due to complete success on the pressure/vacuum tests I don't plan to mess with the seals either since I won't be disrupting them for a top end rebuild. There are no oil or fuel mix leaks anywhere, so I see no value in replacing any of the body gaskets. I think any job doing is worth doing right, but I don't believe in replacing parts 'just because'. Since I don't see any value in replacing the bearings or seals I don't plan to do so. I know some folks disagree with this, but since it has completely tested out I think it's a solid decision. Also, I will obviously be thoroughly testing it post-rebuild as well.
It's quite an impressive machine and I'm excited to cut with it! I wrote this to share my experience, but based on what I've seen so far in the forum there is a good potential for criticism and heated discussion. I do welcome any sound advice or suggestions though realted to my game plan. I'm always interested in learning and want to do this project the right way.
also a newbie, put my first piston in a scored but cleaned cylinder and ran the crap out of it for about a month, thought it ran stronger than new but last w/e heard a funny noise and tore it down to find I had lost a circlip and damaged the intake side so I'm doing a full replacement now. IMHO the exhaust side looke a lot better than it did on day one, I know it was probably out of round but if someone had not known the history I don't think they would have known. Saw was 036 Pro and I don't sell on eBay
UPDATE - haters be hatin'...
Well, I have an update. Despite some folks with pointed warnings I did what I planned to do and had some fun with this saw WITH the scored piston & cylinder. As I had mentioned, it passed all pressure and vacuum tests prior to use. It ran great with a proper tune and made right at 150 psi.
I took it to the Indiana GTG this past Saturday. We're not talking about months of use here, but it got some good solid run time by myself and a few others at the gathering. We didn't take it easy on the saw and near the end of the cookie-cutting when we decided to get all the wood cut up for neighbors who burn for heat I ran it for nearly a half-hour without turning it off. That was cutting 3'+ diameter wood most of that time with a 47" bar and full throttle cut after cut.
Tonight I put the compression tester on it and pulled the muffler to inspect the pistion. It still makes right at 150 psi, and here are the before and after photos of the exhaust side of the piston...
BEFORE GTG
View attachment 296995
AFTER GTG
View attachment 296997
I plan to run it more as-is, so we'll just have to wait to see if even more run time has any effect. So far, so good though - if I hadn't ever pulled the muffler you'd never know there was anything wrong with it...
Well, I have an update. Despite some folks with pointed warnings I did what I planned to do and had some fun with this saw WITH the scored piston & cylinder. As I had mentioned, it passed all pressure and vacuum tests prior to use. It ran great with a proper tune and made right at 150 psi.
I took it to the Indiana GTG this past Saturday. We're not talking about months of use here, but it got some good solid run time by myself and a few others at the gathering. We didn't take it easy on the saw and near the end of the cookie-cutting when we decided to get all the wood cut up for neighbors who burn for heat I ran it for nearly a half-hour without turning it off. That was cutting 3'+ diameter wood most of that time with a 47" bar and full throttle cut after cut.
Tonight I put the compression tester on it and pulled the muffler to inspect the pistion. It still makes right at 150 psi, and here are the before and after photos of the exhaust side of the piston...
BEFORE GTG
View attachment 296995
AFTER GTG
View attachment 296997
I plan to run it more as-is, so we'll just have to wait to see if even more run time has any effect. So far, so good though - if I hadn't ever pulled the muffler you'd never know there was anything wrong with it...
