Hi all. So tonight I went to pick up a Ryobi chainsaw case I found online. With the $10 purchase, the gentleman threw in 3 screnches, and the 40cc Ryobi saw with 18" bar and chain! Told me the saw did not run, and his friend said it wasn't worth fixing. So, before I strip it for parts (as was my main intention), I wanted to just try saving the piston. I know it will probably not work, but just want to try it for fun and to kill some time in teh garage. I have read many topics on how to clean and save the cylinder, and a couple on the saving of pistons. My main question is what would one use to 'clean up' the slight ridges on the piston? I am assuming sandpaper, but what grits would I need. I do not yet have a picture as I just quickly removed the muffler to see and reassembled it. I will be disassembling the saw hopefully tomorrow to try to fix it up. Once I get it torn apart, I will take pictures. Thank you
Saving Scored Piston
- Thread starter lil171
- Start date
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Use a small fine flat file like one for the chain, 6" . Stay away from the sand paper . Before and after . Some buffing pads for finish
Yes on the scotch brite. Sand paper will embed in the soft piston. Just go lite with the file and take the hard spots off, you can feel them with the file. Good luck and if you need help please ask
Huskybill
Addicted to ArboristSite
What diameter is your piston?
What diameter is the piston pin?
What length is the piston?
How far is the top of the pin hole to the top of the piston?
Maybe we can match it with another piston? Some pistons are $10?
What diameter is the piston pin?
What length is the piston?
How far is the top of the pin hole to the top of the piston?
Maybe we can match it with another piston? Some pistons are $10?
That would be great if we had a piston information chart that could help us find a new piston for some of the saws that are out of parts
Just file it off and put new rings
Brent Nowell
Addicted to ArboristSite
i think the biggest thing to watch out for is a change in piston diameter when restoring a used one. The skirt is the part that wears the most in which if it is out significantly you will hear it slap on the cylinder wall when running. Eventually it breaks.
I’ve also been told that the ring grooves can wear as well, causing excessive play in the ring (up and down). I have not seen this myself but maybe on really well worn pistons.
With that in mind I think that’s a fun project, try and restore the in restorable without new parts! See if you can do it
I’ve also been told that the ring grooves can wear as well, causing excessive play in the ring (up and down). I have not seen this myself but maybe on really well worn pistons.
With that in mind I think that’s a fun project, try and restore the in restorable without new parts! See if you can do it
There was a time when I saved about a hundred pistons and refused them. They can be shot peened or knurled with great success, but it does take some effort. The skirts can hold lubrication better, but all good things do not last forever. Thanks
Ok. So today I removed teh piston assembly from the engine. It was scored more than I originally thought. However, I lightly filed the outside of it where it was burred, then followed up with a light scuffing with ScotchBrite pad. I reassembled it, and gave it a quick try. With NO success. However, to me, and my father that came over, teh cylinder was actuall pretty good, but I am not too sure as I am new to all this. The cylinder has a couple lines visable, but we were unable to actually feel anything. I will try a compression tester tomorrow to see what I actually have in it. If it does not run, I am fine with it as I did not expect it to, but rather I had a bit of fun trying to save it and learn more about saws. It was fun to kill some time and get the hands a bit dirty..... Anyways, here are a couple pictures and maybe you can see something I cannot and I may try taking it apart again. Thanks.
Did you get all the aluminum removed from the cylinder
Terrence Jefferson
ArboristSite Operative
If you run a hone gently in the cylinder you can clean that up . Did you replace the piston rings? Looking at the cylinder a set of new rings and it should run.
Firstly, no, I did not remove any aluminum. I wiped it out and nothing came out, as well as I did not honestly feel anything. there. I do want to try teh acid thing one day soon though. Secondly, I did not run a hone down teh cylinder, as I do not have one, and nobody I know has one that small. No, I did not replace the rings. I wish I took a picture of them, as they did look in great shape and no visable scratches on them. However, with that said, I will be tearing it down again and will try the acid carefully in the cylinder, and will take a really good look at the rings with magnifying glass to be sure. Or is there a possibility that they would be damaged in some way not visable? Thank you all for your help and encouragement.
Terrence Jefferson
ArboristSite Operative
The rings will be under sized due to the failure. If you do a compression test on it I would bet you find some low compression I'm guessing around 75-80 psi. The said thing is for aluminum transfer. Your cylinder doesn't appear to have any aluminum transfer in it so I wouldn't try the acid in it. In that cylinder you could use the common 3 stone hone in it and just be careful. Good luck and great little experiment.
And just another observation I wanted to note. I did notice that teh engine is a Zenoah engine. Where would one get rings for this type of engine, if they are indeed need to be replaced? Thanks again.
May I ask why or how the rings would be undersize due to the failure? Just trying to understand. When they were put back on, they moved freely, as well as they were a fair bit larger around than the piston. Just new to this and learning, thanks.
Terrence Jefferson
ArboristSite Operative
If the cylinder is scorn there are only 2 metals on the piston that can do that and the aluminum would most likely transfer to the cylinder so that leaves the rings. The rings may look fine but I bet if you look and feel closely the rings have flat spots on the sealing surface .
Thank you. I will definitely look when I tear it back apart. I will not do such though till I can get my paws on a hone. I will try calling around hopefully this week to see if rings are available locally.
