decomp valves

[314epw]

How do you check out decomp valves for leakage?My 362xp is very easy to start without using the valve.Runs good but I noticed after every cutting there is black residue around the button that you push in.Compression is 130.Can I switch my 359 valve over to the xp for a test or does each valve have a different pressure?
thanks,
Ed

 

[Four Paws]

I am assuming you could switch it over. I would just suggest a plug or short cap screw that you could thread in to seal the decomp valve hole. Just make sure you use the proper thread - it is likely a metric thread. 130 sounds low...

And, the 362 might just be easy to pull over without it. I mean, it isn't a 90+ cc saw. Most saws in that 60-75cc range aren't that hard to pull without a decomp valve.

 

[manual]

You can plug to compare pressure. Afterwards I would put the valve back in.
If the valve is bad could be just a burr or carbon deposits.
Try lapping it like you would a engine valve using lapping compond. If you don't have any try toothpaste "not the gel type". It will work.
the decompression is there not only for easy pulling but also doesn't load you saw down during starts. try to get use to using it and your saw will last longer.

 

[RaisedByWolves]

Take it out and clean out the carbon and try your compression test again.


Could just be carbon fouled.

 

[manual]

Take it out and clean out the carbon and try your compression test again.


Could just be carbon fouled.

Yea silly me that would save time looking for a plug.
Brake or carb cleaner should clean it.

 

[toyotaracer9]

my 359 has the same problem .

 

[begleytree]

The thing that bothers me about this, is if its leaking 'out', it's leaking 'in'
if it's not sealing under compression, you can bet it's sucking air under vacuum as well. IMO, get it checked out. Hate to see a saw burnt up over a decomp valve.
-Ralph

 

[toyotaracer9]

the funny thing is , I havent even used the decompression valve once . and I have around 2 gallons through the saw now . and has done this since the very first tank . I might just try to find a plug that is straight british pipe thread .

 

[Urbicide]

My 359 gets some crud around the decompression valve. However, I don't think it is leaking. It looks more like bar oil mixed with sawdust/dirt residue to me from the chain. It builds up on the seams of the clutch cover too. I can tell a big difference between using the valve and not using it when cold starting the saw.