Intermittent compression? Husky 550xp

[Great_American]

I bought a 2011 550xp from ebay last week.

It started and ran fine for 6 or 7 tanks, but today I noticed something odd. When pulling the cord it was turning over, but it felt like there was very little compression (I hadn't used the decompressor button, and it wasn't engaged). After tugging away for a while I felt the compression return, and it started up. The rest of the day I had no problem getting it going.

 

So my question is; what can cause loss of compression loss when the saw is cold, but fixes itself after some pulling and when the saw is warm?

 

I'm new to chainsaws, and would really appreciate some advice!

 

Thanks

Matt

[H-A]

I would look at the decompression valve.

 

Could have a bit of crap in it.

 

Or loose sparkplug.

 

H-A

[Rich2484]

Short of either the de comp leaking a bit and stopping after the comp has built after a few pulls.

 

Or the spark plug leaking a bit and doing the same as the de comp button.

 

Maybe a compression test will shed some light on it.

[Garyjp]

Piston / piston ring buggered?

Take the exhaust off and take a look for some scoring or wear.

 

Let us know! Curious to know the result. And a pic too if poss

 

 

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[wyk]

Replace your decomp valve and see how she does.

[spudulike]

Could be a ring sticking a little and freeing after a while - the only decomp valve issues I have had are very slight leaks causing neglible loss of pressure or complete failure.

[Great_American]

it was harder than I thought it was going to be, but I managed to get some photos of the piston in various positions:

 

 

Does that look like scoring on the piston, or is some wear normal?

 

How big (expensive) a job is getting the piston replaced?

 

thanks matt

[Rich2484]

Yep that's a new piston, might get away with cleaning the bore up, but will know when you take it apart.

 

Not a tough job, just time consuming.

[SteveA]

Looks like it's scored - I would be taking it apart for a closer inspection.

[Great_American]

Thats bad news.

What causes the scoring?

Can I still use it next week for my 5 day chainsaw course, or is the damage likely to become terminal?