Sthil MS340 Chain tensioner

[Yorkie064]

I volunteer for a local charity and have Lantra award for felling small trees. Problem is I only use the saw a few times a year so not fully familiar with more detail maintenance. Recently I had an issue with the chain tensioner (on this model is simply a screw, guidance block and spigot). I replaced all the parts but I am still having issues after about 5 mins of cutting the chain is visibly slack. Happens with all chains I use. Does anyone know if there a specific method of replacing the tensioner parts on this model or offer advice on what the problem may be. I could put the saw to local dealer but trying to save the charity money.

 

Thanks for your assistance

Dave

[Stubby]

55 minutes ago, Yorkie064 said:

I volunteer for a local charity and have Lantra award for felling small trees. Problem is I only use the saw a few times a year so not fully familiar with more detail maintenance. Recently I had an issue with the chain tensioner (on this model is simply a screw, guidance block and spigot). I replaced all the parts but I am still having issues after about 5 mins of cutting the chain is visibly slack. Happens with all chains I use. Does anyone know if there a specific method of replacing the tensioner parts on this model or offer advice on what the problem may be. I could put the saw to local dealer but trying to save the charity money.

 

Thanks for your assistance

Dave

Make sure the bar is pushed up when you tension it . I do this by holding the saw by the back handle and dropping the bar tip onto a log so that the weight is tending to push the bar up as far as it will go . Check and adjust your tension with it like this . Do the nuts up as tight as you can like this ( enough that the bar wont drop again . ) and then do your final tighten .

[Yorkie064]

Stubby

Thanks for taking the time to reply. The method you mention is standard practices for me but sadly since replacing the components, due to a stripped bolt thread, the chain simply becomes too slack after 5 mins work.

Dave

[Stubby]

2 minutes ago, Yorkie064 said:

Stubby

Thanks for taking the time to reply. The method you mention is standard practices for me but sadly since replacing the components, due to a stripped bolt thread, the chain simply becomes too slack after 5 mins work.

Dave

Oh . ok .  Wonder if everything is assembled correctly ?

[Yorkie064]

Indeed that is my concern...trouble is its simply a screw through a block and into a spigot on which the bar sits. I have tried putting the spigot and one end before screwing the thread through it and tied at the other end before screwing the screw through it but neither works. You can tension the chain initially but as previously mentioned within 5 mins its slack

 

Its a very simple system but I supposed if its not assembled correctly it wont work correctly. Problem is no manuals avavialbe for this or the 360 (which apparently is the same set up.)

[Stubby]

1 minute ago, Yorkie064 said:

Indeed that is my concern...trouble is its simply a screw through a block and into a spigot on which the bar sits. I have tried putting the spigot and one end before screwing the thread through it and tied at the other end before screwing the screw through it but neither works. You can tension the chain initially but as previously mentioned within 5 mins its slack

 

Its a very simple system but I supposed if its not assembled correctly it wont work correctly. Problem is no manuals avavialbe for this or the 360 (which apparently is the same set up.)

I am not familiar with this saw but it sounds to me that possibly something is holding the side cover off a little  not allowing it to clamp down fully ?

[Yorkie064]

Hmm I suspect the chain would not run properly and heaven knows how many times the bar cover has been off but...worthy of investigation...thanks for your thoughts

 

Dave

[Stubby]

41 minutes ago, Yorkie064 said:

Hmm I suspect the chain would not run properly and heaven knows how many times the bar cover has been off but...worthy of investigation...thanks for your thoughts

 

Dave

If it has a floating rim it would run ok . If its a spur maybe not . Just a little tip . When replying to someone you are having a chat with its a good idea to click the quote tab when you reply ( as I have been doing ) that way the person gets a notification .  I dont know when you are replying to me unless I go on that thread and scroll down .

Edited September 4, 2020 by Stubby

[Dan Maynard]

Stubby
Thanks for taking the time to reply. The method you mention is standard practices for me but sadly since replacing the components, due to a stripped bolt thread, the chain simply becomes too slack after 5 mins work.
Dave

The tensioners job is to hold the chain tension only until the bar nuts are done up.

If it's losing tension after 5 minutes, that's not a problem with the tensioner - either the chain is stretching (which will only happen for a bit when new) or the bar is not clamped properly. This could be because the tensioner is not assembled correctly and holding it off.

I'd have thought a trip to local Stihl dealer would be an idea, someone familiar with the saw should be able to set you straight in a few minutes.

[Ratman]

Has it got the metal plate that sits over the studs against the crankcase fitted? It sits between the bar and crankcase, looks like the pic below.