You're entirely fine with a single ring. However, you need to move that ring to the top groove.
Please Help Broke New Piston Ring
- Thread starter tim o
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I was kind of thinking that might be the case. Since the local dealer can get it in 3 days for $5, I'm going to go ahead and get it. But if that wasn't the case its good to know one ring would do it.
This is my first ring job on a chainsaw, I've done them on cars. This thing is almost like working with glass, but now I know. I'll let you all know how the 2nd attempt goes. Thanks everyone.
This is my first ring job on a chainsaw, I've done them on cars. This thing is almost like working with glass, but now I know. I'll let you all know how the 2nd attempt goes. Thanks everyone.
Dman7
ArboristSite Lurker
I believe the correct way to install a ring is to put one end in the groove, and then 'wrap' it around the top of the piston. Do NOT spread the ring and try to insert it all at once in the groove.
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Dman7
ArboristSite Lurker
I've gotten rings to install using both the wrap method and spread method, but I've only snapped rings using the spread method.
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I always wrap them around.
You can break a ring doing either. The wrap method is not recommended in automotive applications. I say it's a chainsaw so any way you can get it on without breaking it is fine. The wrap method does twist the ring though. I cant say one method is more likely to break than the other but think the spread method is easier if you have a tool. It's comes down to preference.
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Either way, you should buy it dinner first.....
Dman7
ArboristSite Lurker
Don't try to put the bottom ring all the way to the bottom groove initially. Wrap it into the top groove, then wrap it to the bottom groove.
Big_Wood
westcoast dweller
i'm actually not even sure if the 251 has a decomp. i don't really work on homeowner stihls. it actually looks more like a burn hole.
IMO it's detonation.
Chitty gas, or a wee bit of diesel either left in the can, or a fuel truck delivery mistake.
Low octane fuel exploding way before it get to the top and ignites before the spark does it. The heat can't dissipate quick enough.
All I ever see water do is strip the chrome off the intake side of the cylinder, or make the saw die.
Chitty gas, or a wee bit of diesel either left in the can, or a fuel truck delivery mistake.
Low octane fuel exploding way before it get to the top and ignites before the spark does it. The heat can't dissipate quick enough.
All I ever see water do is strip the chrome off the intake side of the cylinder, or make the saw die.
I gently and slightly twist the piston back and forth about a 1/4" as I'm installing it. This gets the ring end up against the locator pin, then help the opposite side of the pin compress with a small dull screwdriver. If it won't go in, then be patient and pull it out and start over. Also a slight deflection (cocking it ever so slightly to one side), helps.
That's what She said.
That's what She said.
One little trick I've used before is to use one of the old rings in the lower groove, assuming the old ring isn't too beat up and put the new ring in the upper groove. You can carefully spread the ring with your fingers as long as you don't try to spread them too much. I use a automotive radiator hose clamp as a ring compressor using lots of oil on the ring and inner part of the clamp and not tightening the clamp too tightly. I've seen some Stihl saws that don't require a ring compressor, an MS250 comes to mind..hard to use a compressor in some Stihl saws like a MS290 because of the taper, you can't get a ring compressor in there, I carefully use a screwdriver in that case.
brandonstc6
Addicted to ArboristSite
I've done that before twice. Once on an 032 with stuck rings and a ms170. The 032 rings weren't wore out and the ms170 used ring was close to spec on ring gap but worn. It worked fine both times.
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Don't use a screwdriver or any sort of hard metal tool to compress the ring while installing the piston. If it slips there is a good chance you will gouge the piston.
Make a tool out of the handle of an old tooth brush, by filling it down to a screwdriver like tip. It will never gouge the piston and the brush end is still handy for cleaning things. Keep it in your saw tool kit.
It also helps to have a fork made of wood to support the piston while installing the cylinder. Sort of like a big tuning fork that rests on the case and holds the piston skirt as you work the piston/rings into the cylinder. I made mine out of a scrap of oak board and that also stays in my tool kit. You can make both of these tools in 10 minutes if you have materials, some files, a drill, and a jig/coping saw.
I posted pictures of these tools years ago on a 036 rebuild I did but they got lost when the server here crashed. I don't have them on this computer or I would post them again. I'll see if they might be on one of my old hard drive backups, or if I have the time take some new pictures.
One other thing. Sometimes if you are not experienced installing rings, it helps to have three, or four hands, doing the job.
Make a tool out of the handle of an old tooth brush, by filling it down to a screwdriver like tip. It will never gouge the piston and the brush end is still handy for cleaning things. Keep it in your saw tool kit.
It also helps to have a fork made of wood to support the piston while installing the cylinder. Sort of like a big tuning fork that rests on the case and holds the piston skirt as you work the piston/rings into the cylinder. I made mine out of a scrap of oak board and that also stays in my tool kit. You can make both of these tools in 10 minutes if you have materials, some files, a drill, and a jig/coping saw.
I posted pictures of these tools years ago on a 036 rebuild I did but they got lost when the server here crashed. I don't have them on this computer or I would post them again. I'll see if they might be on one of my old hard drive backups, or if I have the time take some new pictures.
One other thing. Sometimes if you are not experienced installing rings, it helps to have three, or four hands, doing the job.
Never use a screwdriver or any hard metal tool to compress the rings. If it slips you may gouge the piston. 
Make a tool out of an old screwdriver by filing the handle down to a screwdriver like tip. The brush end is still handy for cleaning things. Keep it in your saw tool kit.
It also helps to have a piston support to stabilize the piston when sliding the cylinder on. Cut one out of a scrap of 1" board, it will look like a big tuning fork. The fork rests on the case and goes around the rod, it supports the piston skirts. I made mine out of a scrap of oak board, and keep it in my tool kit.
You can make both of these tools in ten minutes if you have the materials, a file, drill, and coping/jig saw. I posted pictures of these tools here, as used on a 036 rebuild years ago. The pictures got lost, along with all the others, when the server here crashed. I'll see if I still have the on one of my old HD backups.
Also, sometimes it helps to have three, or four hands, if it's your first few times doing rings.
Buy the extra hand a beer.
Good luck.
P.S. before you slip the ring on the piston, check the end gap
P.P.S. sorry about double post, the first one did not show up initially
Make a tool out of an old screwdriver by filing the handle down to a screwdriver like tip. The brush end is still handy for cleaning things. Keep it in your saw tool kit.
It also helps to have a piston support to stabilize the piston when sliding the cylinder on. Cut one out of a scrap of 1" board, it will look like a big tuning fork. The fork rests on the case and goes around the rod, it supports the piston skirts. I made mine out of a scrap of oak board, and keep it in my tool kit.
You can make both of these tools in ten minutes if you have the materials, a file, drill, and coping/jig saw. I posted pictures of these tools here, as used on a 036 rebuild years ago. The pictures got lost, along with all the others, when the server here crashed. I'll see if I still have the on one of my old HD backups.
Also, sometimes it helps to have three, or four hands, if it's your first few times doing rings.
Buy the extra hand a beer.Good luck.
P.S. before you slip the ring on the piston, check the end gap
P.P.S. sorry about double post, the first one did not show up initially
ANewSawyer
Addicted to ArboristSite
I haven't replaced any rings with new. Pulled old rings off though but by the grace of god haven't broken one. I am real easy on the rings. Is installing new rings harder than removing old rings?
Dman7
ArboristSite Lurker
Yes, it's much harder if you snap them in two [emoji854]
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