Is this what a leaking decompression valve looks like?

[Muddy42]

 

 

This is on a one year old Husqvarna brushcutter 555rxt that has been used a lot.  I was doing some routine maintenance after it became a bit harder to start.  I have replaced the decomp valve with a plug to see if that makes a difference. I appreciate that you get some oil on the decomp valve but this seems excessive?

 

Edited July 26, 2023 by Muddy42

[Muddy42]

[Stubby]

2 hours ago, Muddy42 said:

Was it screwed in properly ? You can usually tell from the tapered seat of the valve but you have to take it out to see that . What did it look like when you removed it ? What I mean is it looks like its been leaking from the thread rather than the seat of the valve ...

Edited July 26, 2023 by Stubby

[spudulike]

Put some bubbly water around it and pull the engine over slowly and see if you get bubbles. 

The decomp can be re-ground in with grinding paste but clean it afterwards. 

It looks like it may have been leaking or just used a fair bit.

[doobin]

9 hours ago, spudulike said:

Put some bubbly water around it and pull the engine over slowly and see if you get bubbles. 

The decomp can be re-ground in with grinding paste but clean it afterwards. 

It looks like it may have been leaking or just used a fair bit.

This is a bit extravagent, but handy to have about the place. Soapy water substitute in a handy aerosol.

 

Action Can LD-90 Gas Leak Detector  500ml | Toolstation

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Gas leak detector spray for safety checks on all types of gas systems, including oxygen. Highlights leaks even on...

 

Edited July 27, 2023 by doobin

[Muddy42]

11 hours ago, spudulike said:

Put some bubbly water around it and pull the engine over slowly and see if you get bubbles. 

The decomp can be re-ground in with grinding paste but clean it afterwards. 

It looks like it may have been leaking or just used a fair bit.

 

Thanks.  Definitely used a fair bit.

13 hours ago, Stubby said:

Was it screwed in properly ? You can usually tell from the tapered seat of the valve but you have to take it out to see that . What did it look like when you removed it ? What I mean is it looks like its been leaking from the thread rather than the seat of the valve ...

 

Thanks.  Its really hard to tell.  I'm leaning slightly towards it leaking at the thread than the valve, but the whole thing was covered in oily soot.  I'm going to clean it up and try again.  I get that the valve might leak a bit if used, maybe i'll see if it still leaks when I don't use the valve.

[tenner]

Whip the decomp out and check it on a pressure tester.

 

Pretty sure it was a leaky decomp which killed my beloved Oleo Mac 

 

[spudulike]

You can do a pressure and vacuum leak down test to test the thread and valve. I did find a lot would leak slightly but as I said, I ground them in with fine valve paste, cleaned, oiled and refitted them which worked for me.

[Muddy42]

I think I'll just leave the plug in for now as it starts easily enough without the decomp valve.