Stihl ms261 decompression valve

[stuking94]

Hi, just got a quick question about the decompression valve on the Stihl ms261, I doubt I'll ever really use it so was thinking about buying a blanking plug for it, has anyone else done this or are you better off just leaving it? I've always wondered if decompression valves could potentially start to leak over time. Thanks.

 

[Shibby]

People plug them all the time. They will leak at some point, maybe 10 years from now maybe tomorrow. I personally leave them on my saws and replace them when leaking.

 

[stuking94]

People plug them all the time. They will leak at some point, maybe 10 years from now maybe tomorrow. I personally leave them on my saws and replace them when leaking.

Cheers mate

 

[Int1968]

I’ve seen em leak or get stuck open, on the Arctic 261 mike CFB just built me I had him remove and install a plug. I might eventually try and find a rubber plug for the plastic. I think the husky in the side is a better design.

 

[Wood Doctor]

I’ve seen em leak or get stuck open, on the Arctic 261 mike CFB just built me I had him remove and install a plug. I might eventually try and find a rubber plug for the plastic. I think the husky in the side is a better design.

Most common failure is that the plastic top cap gets broken off or the shaft bends. I know some men who never use them, so I keep a supply of plugs on hand. Occasionally I have run into a saw that was bought used and the plug was there already. The owner didn't even know what it was there for. On the other hand, one guy running a Husqvarna 350 didn't even know that the decomp valve was there nor what its purpose was.

 

[Wonkydonkey]

I’ve used it to stop a saw when the on/off switch wasn’t working at times. Bu5 that’s just using what you can, when you have to..

 

[Wood Doctor]

I’ve used it to stop a saw when the on/off switch wasn’t working at times. Bu5 that’s just using what you can, when you have to..

Makes me wonder why the saw MFG doesn't say in the owners manual, "You can use the decompression valve as an emergency kill switch."

 

[Stu94]

Cheers for input guys

 

[Funky sawman]

Makes me wonder why the saw MFG doesn't say in the owners manual, "You can use the decompression valve as an emergency kill switch."

Probably because it doesn't always work. I know a stock ms460 I sawed with ran 180 psi so with the decom valve pushed it still had at least 120 psi, which in this saws case it would idle all day with the decom pushed in. I know this because a widow Maker came down one day and hit the top cover on that saw, bending the decom valve stem, causing it to be stuck open. Being one hour from the end of my shift, I ran the saw like this the remainder of that day.

 

[drf256]

Nothing wrong with decomp valves. I wish all saws had them.

I use them for every start. Even though they really aren’t needed on saws (ported) under 70cc IMHO, I find nothing wrong with an easier start with less wear and tear on the starting system.

My own ported MS261 will get ripped from my hand if I don’t use the decomp and don’t start it like I mean it, even warm. If I press the decomp it’s a quick 2 finger start. Little saws have 2 issues with starting if high compression. One is the perception that it’s so small it’s a joke to start, the other is lack of weight for the inertia of a drop start.

Then there is the myth that they will leak and lean a saw out to the point where it fails. If someone can explain this to me I am all ears. At what point exactly with the end of a decomp valve in a cylinder become under negative pressure/vacuum in a running 2T engine?

Even though I can start a saw without a decomp it doesn’t mean I want to.

 

[rogue60]

Nothing wrong with decomp valves. I wish all saws had them.

I use them for every start. Even though they really aren’t needed on saws (ported) under 70cc IMHO, I find nothing wrong with an easier start with less wear and tear on the starting system.

My own ported MS261 will get ripped from my hand if I don’t use the decomp and don’t start it like I mean it, even warm. If I press the decomp it’s a quick 2 finger start. Little saws have 2 issues with starting if high compression. One is the perception that it’s so small it’s a joke to start, the other is lack of weight for the inertia of a drop start.

Then there is the myth that they will leak and lean a saw out to the point where it fails. If someone can explain this to me I am all ears. At what point exactly with the end of a decomp valve in a cylinder become under negative pressure/vacuum in a running 2T engine?

Even though I can start a saw without a decomp it doesn’t mean I want to.

Yep the good old a leaking decomp burnt up my saw myth lol
It's impossible for a running 2T to pull air in through the decomp.
Leak air out yeah but pull air in no, like Funky sawman said he had one stuck open with no ill effects.

 

[wap13]

I used to not use a decomp on anything from my 261 to 661. I had no need for it. And as far as being able to get a saw started I still dont "need" it. However I now use them on all my saws simply to save the starter/starting assembly some wear and tear.

 

[huskihl]

Removed the decomp on my Smurf 7900 once. Thought the blue flames shooting out the side were cool so I carried on and cut a couple cookies with it. Saw didn’t burn up. @davidwyby owns it now

 

[davidwyby]

Removed the decomp on my Smurf 7900 once. Thought the blue flames shooting out the side were cool so I carried on and cut a couple cookies with it. Saw didn’t burn up. @davidwyby owns it now

I need to try that