Chain and bar replacement

[chase]

I'm using a Stihl Wood Boss MS270 and I've noticed recently that my chain seems to loosen immediately after cutting for just a few minutes to the point that it hangs below the bar, I'll tighten it and it will do it again. Is this a sure sign that the chain needs replaced? How do you know when the bar needs replaced?

 

[turnkey4099]

I'm using a Stihl Wood Boss MS270 and I've noticed recently that my chain seems to loosen immediately after cutting for just a few minutes to the point that it hangs below the bar, I'll tighten it and it will do it again. Is this a sure sign that the chain needs replaced? How do you know when the bar needs replaced?

Chains stretching that fast are usually caused by either a very dull chain or lack of oil. If the chain/bar are very hot after 'just a few minutes' I would bet on one of the two possibilities.

Harry K

 

[JackD_ME]

I'm with him^^^.
If you have a dealer nearby get the little "pocket guide" on Stihl bars & chains, how to sharpen them and when to replace them.
Should be free!

 

[echoman8]

I'm using a Stihl Wood Boss MS270 and I've noticed recently that my chain seems to loosen immediately after cutting for just a few minutes to the point that it hangs below the bar, I'll tighten it and it will do it again. Is this a sure sign that the chain needs replaced? How do you know when the bar needs replaced?

Hi, I have been posting on lawnsite. This is my first post here.

There are three things that affect the chain tension and also cause it to slacken quickly. The sprocket on the motor (drives the chain), the sprocket on the bar tip (can become too worn and provide slack) and just as important, the rivets holding the chain together.

Sprocket : If worn, there will be a groove where the chain rides.

Bar : Compare the sprocket at the tip to a new one. If your sprocket tips are pointed instead of blunt, it is worn badly.

Chain : Lay the chain on a flat surface, place your hands about 8 inches apart on the chain. Push the chain together and apart a few times observing the slack in the rivets. There should be some wear, but slightly noticeable.

The most overlooked problem is the chain rivets. In many areas, there are soil conditions where airborne dust or sand is present. This material settles on and grows in the trees all the way to the top branches. As you are cutting, you are cutting through some sand. The combination of bar oil and sand/dust is very close to the consistency of grinding material. The result is metal wear with the weakest point on a saw chain being the rivets.

The end result is: if one or more of the three are worn too much, it throws everything out of pitch (out of whack). One or all should be replaced.

Good luck

de

 

[Bermie]

Make sure you are holding the tip of the bar UP at the same time you are tightening the chain.

If you don't then when you go to cut, the bar will work its way up with the pressure you apply when cutting and the chain will lose tension and hang down.

When you have the saw on the bench and the chain is slack, grab the bar by the tip and move it up and down...see, there is a range of play there! Hold the bar up as far as it will go, probably no more than about 1/4 to 1/2 ", THEN tighten the chain, just till the tie straps meet the bottom of the bar. Tighten the side nuts and check for tension, adjust as necessary.

 

[echoman8]

raise bar

Make sure you are holding the tip of the bar UP at the same time you are tightening the chain.

If you don't then when you go to cut, the bar will work its way up with the pressure you apply when cutting and the chain will lose tension and hang down.

When you have the saw on the bench and the chain is slack, grab the bar by the tip and move it up and down...see, there is a range of play there! Hold the bar up as far as it will go, probably no more than about 1/4 to 1/2 ", THEN tighten the chain, just till the tie straps meet the bottom of the bar. Tighten the side nuts and check for tension, adjust as necessary.

Hi Bermie,

Good post.

I forget the simple things much too often

de

 

[chase]

I appreciate all of the feedback. The chain seems to still be doing this. I plan to totally disassemble and look things over. Anyone have suggestions where I can buy a couple extra chains for a great price?

 

[echoman8]

Chain droop

If everything is in pitch with no excessive wear, it should not droop under normal conditions for an hour or more.

Reinspect the bar (pointed tips on sprocket), chain (rivet wear), and sprocket (groove). More details on post #4.

While adjusting, raise the end of the bar up as suggested before. Also raise bar tip when tightening. If it was not adjusted tight enough, the chain will drop after starting and before cutting wood.

I still believe you have wear somewhere. The bar and sprocket is very obvious but the chain rivets is more subtle.

I buy my chains from Bailey's. There are some good buys on Ebay if you are familiar with brands and style of saw chain.

Good luck
de

 

[Mike PA]

This may or may not apply to you, but another cause of a chain suddenly getting loose is having a bent or stripped adjustment screw. Happened to me once on my Stihl.

 

[Bermie]

Hi Bermie,

Good post.

I forget the simple things much too often

de

Ha, don't we all! Welcome to the site!

 

[chase]

I disassembled the bar/chain. Can someone please post a picture of a new bar tip as well as the sprocket, my sprocket has a groove on the center of each tooth and the tip of the bars sprocket appears pointed but I don't really know what a new one looks like. Thanks for all the help.

 

[Bermie]

Don't have a picture but...

If the groove on your sprocket is more than 2mm deep its time for a new one, and get two new chains while you are at it and start fresh.
Your bar nose sprocket should have slightly blunted teeth, if the teeth meet in a sharp point like a crisp edged triangle, its worn out - get a new one.

 

[chase]

Anyone able to please post a picture of a new sprocket and bar for me?

 

[Lawnmowerboy48]

Are you lining up the tensioner post with the hole in the bar?