De-Compression Valves

[thumbilly]

 

[spindrift7mm]

Most leakage is caused by carbon in the seat so basically the more you use it the better it works. Seems the guys I know that don't use the decomp and don't like them have more trouble with them. On saws I build I test the decomp by simpily shove it in the rubber hose on my pressure tester. All the leakers are rough when you spin the stem which is carbon build up. I've only found one that would not clean up with carb cleaner and a little tapping on the cyl tip to bust the carbon. Most rough ones just need cleaner and spinning. On my own saws anytime I use the decomp I spin it if you can reach it. It's just a poppet valve, no black magic. Ken

 

[thumbilly]

I wondered if the lack of use related to failure. I've discovered the saws that need them don't have them and the ones that have them don't always need them.

 

[G-Man!!!]

Just to make sure everyone understands, I had a used Husqvarna de-comp valve in the cylinder, it leaked air, so I put a new one in that looked just like the used one and the new one also leaked. Next I connected the pressure test hose directly to the de-comp valve, and as I suspected it failed also, leaking air out of the two small holes on the hex nut of the valve body.

 

[Gypo Logger]

I never use a decomp, even on an 088. It's more about body English than anything else.

 

[Hoolio]

I've had a 372 for about 3months, haven't used it much but I pulled it apart to port it, (1st time porting a saw) and noticed the piston was had a little clean patch where the decomp is, I'm guessing it's a leak?
I rarely use the decomp because I actually find it easier to start with comp, (less pulls)
Think il plug it.

 

[spindrift7mm]

I wondered if the lack of use related to failure. I've discovered the saws that need them don't have them and the ones that have them don't always need them.

I think a high comp light saw is toughest to start cause there's no weight to help counter the pull. Toughest starting saw I own is a early MS440 non decomp all stock except tri ported muffler. You gotta sneak up on it and attack the rope. Ken

 

[thumbilly]

The 298xp is a beast to start. Matter of fact just had to put a rope in it last week.

 

[thumbilly]

Also FYI that 555 is just a normal recoil.

 

[spindrift7mm]

The 298xp is a beast to start. Matter of fact just had to put a rope in it last week.

I think saving starter hardware is the main reason for decomp valves. I also put Stihl Elastostart ropes on all big hard starters I build. Get a kick outa die hard Husky guys when they see that Stihl rope. Ken

 

[drf255]

They say some Stihl kick harder on start because if where their timing is set.

I feel that on some models, decomp is ridiculous, like the 026 PRO.

That being said, I wouldn't want my 066 to not have one. It rips the callus off my hands with 160 psi of stock goodness.

It just got some Tennessee bananas added this week, so I can't imagine just how bad it will be at 200 psi to start without a decomp valve.

 

[Definitive Dave]

I guess I have to need to prove anything to anyone. I was just getting at that starting a chainsaw with or with out the decomp. Is low on my list of things that destroy my body.http://tapatalk.imageshack.com/
Regardless of whether you believe me I split this tractor by hand by myself the way I do almost all of them.


v2/15/03/19/830b17d54f96a8bfc6824dd6865c9732.jpg

This was just a lot odd bull work.

uhhm.......psst hey buddy, I think somebody stole some wheels off your tractor
DDave

 

[mijdirtyjeep]

uhhm.......psst hey buddy, I think somebody stole some wheels off your tractor
DDave

Thanks, I almost spit my coffee out on my keyboard

Also, in that pic looks like the second from the top cribbage stack only has one board, would that not make the top board essentially a teeter totter

 

[thumbilly]

I'm fairly certain that there was two. It was awhile ago on that job. But I do recall that was all the crib blocks we had. More now thanks to that job. Also not the set of screw Jacks back farther. I still didn't spend any more time under it than I had to.

 

[mijdirtyjeep]

I still didn't spend any more time under it than I had to.

I agree, I hate being under any equipment sitting on cribbage, just scares the hell out of me!

 

[thumbilly]

I built these to make it a little nicer on the row crop tractors. But there's just no good way on those big articulating pigs.

 

[thumbilly]

Got the 562xp back today. Had it in on warranty the decompression valve was leaking bad. Can't wait to compare those two saws. [emoji38]

 

[flyinghunter]

If you can't get the valve to seal by cleaning and spinning, sometimes a drill on the button with valve grinding paste on the valve seat does the trick.

 

[thumbilly]

It was idling funny and had a hesitation. Still under warranty so I took it to the dealer. I knew it was wet but didn't really think it would cause a huge problem. They checked it out found it was leaking pretty bad. They claim they tried cleaning it and it still leaked so they just put a new one in. No skin off my back. Updated the tune too while they were at it.

 

[CTYank]

One saw I have that could use a decomp, and doesn't have one, is the Dolly 6100. Cold compression 225 psi, on known-good gauge. The "easy-start" thingie on it is no big help when the temps are in the single-digits F. Until it feels like being cranked. Then no biggie.

Worst, nastiest decomp I've encountered was on a 50 cc Pioneer 1074. Had a linkage from the recoil to open the decomp for cranking. Lots of weight on the decomp shaft, so with engine vibes it never really closed. That decomp was on the flywheel side of the cyl., so with constant oil weepage there, and normal chainsaw dust, it quickly built up a thick layer of insulation on the fins. Priceless.

Moderate compression engine, so no mo decomp. Shelf queen anyhow, with only moderate power at best. Not mine, thankfully.