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KUDOS (Solved) Decomp hissing on 390xp

HumBurner

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I did some searching last week on the matter and thought I'd found the answers, but now I'm not so certain.

Have a well-used 390xp. Took it out of its box a couple weeks ago and noticed the decomp valve was hissing when pushed in and pulling on the starter rope. It's been almost two years since I've run the saw and didn't recall the hissing.

My searches led me to order a new, OEM decomp. I installed it the other day at lunch. The valve stem seemed tighter. It also hisses when decomp is pushed in. Some posts said this will happen, some say faulty decomp, etc.

Saw has stout compression with decomp released and is tough to pull over. No hissing when trying this. Still passes the drop test, but I haven't thrown a tester on it for numbers.


So, my question is: Is the decomp supposed to release a little air when pulling over with it pushed in? Is this hissing normal?

I asked my crewboss to check his 288/394 if he gets a chance. He said he thought he remembered his hissing, but couldn't recall for sure.


Unless faulty, I'll keep the new decomp installed and see if I can't find a way to deep clean the old one to keep as a backup.



Thanks for any input.
 

ammoaddict

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I did some searching last week on the matter and thought I'd found the answers, but now I'm not so certain.

Have a well-used 390xp. Took it out of its box a couple weeks ago and noticed the decomp valve was hissing when pushed in and pulling on the starter rope. It's been almost two years since I've run the saw and didn't recall the hissing.

My searches led me to order a new, OEM decomp. I installed it the other day at lunch. The valve stem seemed tighter. It also hisses when decomp is pushed in. Some posts said this will happen, some say faulty decomp, etc.

Saw has stout compression with decomp released and is tough to pull over. No hissing when trying this. Still passes the drop test, but I haven't thrown a tester on it for numbers.


So, my question is: Is the decomp supposed to release a little air when pulling over with it pushed in? Is this hissing normal?

I asked my crewboss to check his 288/394 if he gets a chance. He said he thought he remembered his hissing, but couldn't recall for sure.


Unless faulty, I'll keep the new decomp installed and see if I can't find a way to deep clean the old one to keep as a backup.



Thanks for any input.
Yes, the purpose of the decomp is to release a little air so it's not so hard to pull over. I have seen them with different size holes, I assume for different size engines. I have never noticed any of mine hissing but I have never listened that close. As long as it's not leaking while it's running, I wouldn't worry about it.
 

Duce

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Pull decompression valve out and pull it over slowly, you will hear no hissing. You closed the decompression port, open the port and you get hissing from letting air our, as stated, that’s how it works.
 

Seachaser

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Pull decompression valve out and pull it over slowly, you will hear no hissing. You closed the decompression port, open the port and you get hissing from letting air our, as stated, that’s how it works.
Is it common for a decomp to pop out after every pull.
 

HumBurner

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Thanks for confirming yall.

Oddly, both 562s had no real sound of air using their decomps. I'll pay attention next time i fire up my other few saws with decomps.
 

Agrarian

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I believe the 562 decomp valve does not have a visible vent port which is why you may not hear it release air when pressed in. Plus, being mounted in the top of the cylinder, the 562 valve vent, like other valves mounted in the top of the cylinder, is tiny. Most (all?) earlier decomp valves have visible vent ports in the hex base of the valve, making the likelihood of hearing them vent greater. Adding to this, the decomp valve used on the 394 uses a valve with the largest vent port Husky makes, also increasing the likelihood of hearing it.
 

cus_deluxe

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I believe the 562 decomp valve does not have a visible vent port which is why you may not hear it release air when pressed in. Plus, being mounted in the top of the cylinder, the 562 valve vent, like other valves mounted in the top of the cylinder, is tiny. Most (all?) earlier decomp valves have visible vent ports in the hex base of the valve, making the likelihood of hearing them vent greater. Adding to this, the decomp valve used on the 394 uses a valve with the largest vent port Husky makes, also increasing the likelihood of hearing it.
very well said.
 
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