Stihl MS271 Problems

[clake4341]

Hello all glad to be a part of this group so here is my problem well really I have 1 major problem 1 minor problem and a lot of questionsbut first the problem
I have a scored piston on my ms271 which I'm told needs a complete rebuild now I can get the piston kit but I'm having a problem with the cylinder and Looking at after market equipment it appears the OEM parts would cost the same as a new chainsaw so does anyone know where I can get AM cylinder for ms271 and my next question would be could I install AM MS261 piston and cylinder kit in a MS271 housing . sounds weird but some people have indicated I can down grade but I cannot up-grade does anyone know if this is true because I am at a stand still and not sure what to do..

thanks

 

[Bob Hedgecutter]

First question- how did you come to own a 271 with a scored piston? Was it straight gassed or was it run lean, had an air leak?
Next question, can we have detailed photographs of the interior of the cylinder?
It could well be that you have transfer from the melted piston on the cylinder walls- but if it has not gone through the plating of the cylinder interior, the cylinder most likely can be cleaned up and saved to be reused with a new piston and rings.

Pretty sure the oddball 271 cylinders are not available as an aftermarket replacement, so the easiest out is to save your old one.

261 and 271 share the same piston- so yes you can use a piston marked as a 261 piston in a 271 cylinder- same 44.7mm bore.

 

[clake4341]

Well I have had this 271 for about 6-7 years my dauther bought this for me after my old died after 40 good years of service. I have always used premixed 50:1 fuel from a stihl dealer and I think the last couple of times I had the premixed fuel probable over a year old so I think the gas oil mixture turned to less oil amd more fuel. I have taken the machine down and removed the cylinder and you are right it does look like I could have melted transfer so I am going to try and clean it up using very fine paper and hopefully I can save the 271 from going for parts. Thank you for your response also the 271 tear down was not as easy as it looks on youtube and hopfully get it back together will be easier I will let everyone know how I make out with this hopefully delivery time for the new parts won't take to long

 

[Bob Hedgecutter]

Well I have had this 271 for about 6-7 years my dauther bought this for me after my old died after 40 good years of service. I have always used premixed 50:1 fuel from a stihl dealer and I think the last couple of times I had the premixed fuel probable over a year old so I think the gas oil mixture turned to less oil amd more fuel. I have taken the machine down and removed the cylinder and you are right it does look like I could have melted transfer so I am going to try and clean it up using very fine paper and hopefully I can save the 271 from going for parts. Thank you for your response also the 271 tear down was not as easy as it looks on youtube and hopfully get it back together will be easier I will let everyone know how I make out with this hopefully delivery time for the new parts won't take to long

If you are positive the saw was only ever run on canned premix fuel- odds are pretty good the saw may have developed an air leak that took out the piston and it will NEED repaired before any new top end is fitted- or it will do the exact same again.
Ideally, some form of pressure and vacuum test should be done using the old cylinder to check for air leaks at all possible entry points.

Agreed the 271-291 is not the easiest saw to work on

 

[clake4341]

Well I have dis-assembled the machine which was quite a job so I am pretty sure the old piston is NOT going back in I will do a compression test once the new piston and rings are installed and hopefully everything will be ok. When you say air leaks?? when I do compression test does the pressure need to stay constent IE: say I get 135psi should the reading stay for a length of time??

 

[Bob Hedgecutter]

Well I have dis-assembled the machine which was quite a job so I am pretty sure the old piston is NOT going back in I will do a compression test once the new piston and rings are installed and hopefully everything will be ok. When you say air leaks?? when I do compression test does the pressure need to stay constent IE: say I get 135psi should the reading stay for a length of time??

Photos of the piston and the interior of the cylinder will help no end.
No, a compression test holds pressure outside the cylinder and within the gauge and hose itself. It gives an indication of the combustion side of the cylinder only. Air leaks that lean a saw out happen below the top of the piston and the combustion chamber- from intake boots, impulse lines, cylinder gaskets, clamshell pans and main oil seals. They require another type of gauge, port block offs and a means of entry into the crankcase to test.
Ideally you have to figure out why the piston was trashed in the original set up and correct it- or a new piston will just tear itself up again in a very short period of time.