Stihl 460 Decompression Valve Problem - I think!!!

I seem to have developed a "problem" with my 460's decompression valve. The valve (as well as those on my 360/038/440) have always worked in what I considered to be the proper fashion .................. the valve stayed depressed regardless how many times you pulled the starter, until the engine gave some type of firing. It needed some type of "cough/ignition" to raise it back up. A few days ago, my 460 started popping up the decompression valve after every cord pull. Its a well used machine, so I figured it probably was time for a new valve (versus some other problem) and bought one. I installed the new valve, only to have the saw do the same thing .................... the new valve is popping up on every cord pull too.

Assuming that this is not its correct operation, and that the new valve is not defective, could there be something else causing this to happen?

 

Make sure its right. I had my vale acting up on my 390 and the thing started tick I g and then fell apart into the cylinder wedging itself between the piston and the cyl lock I g up the saw. Luckily no damage was done and the saw still runs after reassembly. and a new valve

 

I have half a mind to install the factory plug on them . I rarely use them after that episode. Use to always use it but now am leary.

 

I have to push mine after every pull on both my Stihl saws and that has been my experience with others as well.

 

I have a stihl 390 and 650. The valve only closes each time the motor pops/fires. If it do sent fire I can pull pullpull. Like if I leave the switch I. Off. I can pull till may arm falls off and it not close the valve. Once I let it fire it closes.

Less experience with the husky 372xp but the times I have used it are the same.

 

I haven't done any work on it Dex other than the recent flywheel/starter repairs I posted about. I can't see where that would have affected anything, and the saw worked fine after that for 2 tanks before it started the decomp issue. I did notice that the plunger on the new valve seemed to move even easier than the plunger on the old one. I think I'm going to use the old "parts swap" methodology to investigate further here ...................... I'll swap out the "working valve" out of my 440 with the 460 and see how they work after that. That should tell me if its a valve or saw issue.

 

Plugging it might work on a smaller saw like a 260/360 ........................ but my 58 year old wrist does not relish the thought of trying to start that 460 without one! I'll let you younger guys go that route!

 

My BIL's 441 pops the valve on every pull. He had the dealer replace the valve and it did the same thing. I think it just has a crapload of compression.

 

Trying to start. My 650 i gave it a sissy pull onetime and over stressed my elbow. And it was hurting for a few days.

 

Does it pop up even if you pull it with the switch in the off position? If the key had fallen out when you were replacing the flywheel, and the flywheel had since shifted a bit, throwing off the timing just a little... Oh, who am I kidding? I have no idea what I'm talking about.

 

Actually, Dex and Lukem might be onto the right issue here regarding compression, although my buddy has my tester at the moment so I can't tell what it is now. Some of you might remember that I changed the piston/rings in this saw last summer after poking a hole in my piston with a "piston stop tool". When I think about it, I probably have only put 6-7 tanks through it since that time since I'm usually using smaller caliber weapons in my arsenal. Maybe the rings have finally seated to the point that I'm now getting that "crapload" of compression that caused the change in performance of the decomp valve? I still don't think valves are supposed to pop up all the time like this, but it may at least explain why I'm now seeing the issue.

 

OEM MM. I just returned from my dealer. I showed him the old/new valves and how the new one he gave me had even less resistance than the old one. He did not have another in stock to compare with, so he ordered one that will be here Friday. We'll see how it compares when it comes in, I'll post a follow-up then.

On a 460 related note, I asked him what was the standard size rim for my saw (from another post). He said it was 8-pin, not 7 ........................... at least for the 460 "Mag" via the diagram he had up on his screen. Maybe the older 046 and earlier "plain Jane" 460's were 7-pin standard, but the "Mag" is definitely considered 8-pin.

 

The screen shoes all options in the IPL.

Its funny when I go buy parts for the 650 they always ask "magnum" and I say just like MM said. All that is is a sticker there all magnum???

 

That's exactly what my dealer just asked me about my 460 an hour ago ....................... "Is that a Magnum". I have always thought there were earlier ones a few CC's less as per many of the other Stihl lineups. You guys are so much more knowledgeable than those guys behind my local counter!!!!!!!! Now you see why I usually order OEM cheaper from the internet! I even asked the guy "are you sure 7-pin is not standard and 8-pin optional". He looked at his IPL diagram again and said "no, 8 pin is standard". Dealers ................................................. Arrrrrrrrrrrrrrggggggggggggggggg.

 

There's no way I'd be able to constantly start my 460 without the decomp. It would break the starter or rope.
The 660 isn't so bad though, dunno why. Both saws run around 180-190psi.

I've never had the decomp always stay open, even on a brand new Stihl. I'm hardly a saw expert but I really doubt all the saws I've used where defective!

 

By "open" I assume you are meaning "down". That's why I started this post, to try and find out what is the "proper" operation and whether I had a "problem" or not. I can only speak from the experience with my 360 Pro/440 Mag/460 Mag .................... they always stayed open, regardless how many times you might pull them, until some type of cough/pop/ignition to force them up and close them. However, from the posts so far, it appears there is definitely some variability in operation among the posters.