Husqvarna 560: part seized?

[waterbuoy]

Rest assured I am equally non-PC, hence my question - which was meant to be light hearted.  Hopefully no offence taken!

[Mark_Skyland]

On 10/01/2023 at 09:08, richvdh said:

Thanks to everyone who offered advice so far.

 

I've got the saw back and opened it up. Pictures attached.

 

As you can see, the piston is heavily scored, though only on the exhaust side, which I found interesting, but anyway.

 

Troublingly, the cylinder also seems to be pretty scored on the exhaust side (again, it's still shiny on the intake side). Opinions as to whether it's likely to be salvageable, or whether I should cut my losses with an aftermarket cylinder assembly?

 

I may be wrong but it looks like you may have had an air leak at the base gasket or manifold to cylinder.

Did you do a pressure/vacuum test? Where all the cylinder bolts nice and tight?

[richvdh]

> I may be wrong but it looks like you may have had an air leak at the base gasket or manifold to cylinder.

 

Thanks @Mark_Skyland: what makes you say that?

 

> Did you do a pressure/vacuum test?

 

I was planning to, but the sparkplug socket is teeny-tiny (10mm) and I didn't have an adaptor, so I skipped it. That may have been a mistake :(.

 

> Where all the cylinder bolts nice and tight?

 

Yup, they seemed fine.

[spudulike]

I think Mark is seeing dark staining on the base gasket on the first of your pics. I reckon this is from the saw being flooded from trying to start it with the choke on but needs to be clarified.

The usual place 560s leak was around the front transfers but was resolved in one of the upgrades by the factory. Yours looks fine in this area.

I wouldn't expect a near new machine to have any leaks from the base gasket. The old fuel mix is much more likely.

[Mark_Skyland]

8 hours ago, richvdh said:

> I may be wrong but it looks like you may have had an air leak at the base gasket or manifold to cylinder.

 

Thanks @Mark_Skyland: what makes you say that?

 

> Did you do a pressure/vacuum test?

 

I was planning to, but the sparkplug socket is teeny-tiny (10mm) and I didn't have an adaptor, so I skipped it. That may have been a mistake :(.

 

> Where all the cylinder bolts nice and tight?

 

Yup, they seemed fine.

As Spud says I was looking at the staining on the gasket and also the intake boot looks wet on the last picture.

 

He probably is right in that its just excess fuel as looking again there does look like a fair bit of it on top of the crank.

 

I always carry out a pressure/vac test before and after engine strip downs as you never know if it was a leaking crank seal which I have seen with a few 550xp saws but I dont think I have seen any on the 560.

 

If you have a pressure tester leave the spark plug in, block the intake ports in the manifold and pressurise through the impulse hole. Give the decompression valve a little spin as this can leak slightly and cause false readings.

 

[richvdh]

> As Spud says I was looking at the staining on the gasket and also the intake boot looks wet on the last picture.

>

> He probably is right in that its just excess fuel as looking again there does look like a fair bit of it on top of the crank.

Yup, when I opened up the saw there was quite a lot of oily fuel coating the intake side of the piston, which then ran down and soaked into the gasket.

 

> If you have a pressure tester leave the spark plug in, block the intake ports in the manifold and pressurise through the impulse hole.

 

Good idea. Any idea where I can get a little tapered adapter that will fit into the impulse hole? Google is failing me.

 

I had a brief go at the cylinder with some caustic soda this morning. It seems to have improved matters. Will give it another go over the weekend.

 

[richvdh]

Hi folks, wanted to post a follow-up here.

 

Long story short, I rebuilt the saw and gave it its first proper workout this weekend and it worked beautifully!

 

Following the advice on this thread, I cleaned up the cylinder as best I could with NaOH, then a bit of wet & dry, and finally a cylinder hone; and I fitted a new piston and ring. To do a pressure test, I struggled to get a seal on the intake with homemade plates: it's a funky shape with several different channels. In the end I just spent £10 on the Husqvarna service tool and connected the pressure tester to the spark plug hole.

 

Compression and pressure tests were both good so I fed it some Aspen Alkylate fuel and it seemed to be running happily, so at the weekend I took it out to the wood and used it for a couple of hours with no problems at all.

 

It's a lovely saw when it's working right! Thanks to everyone who offered advice here to help me salvage it.

Edited February 7, 2023 by richvdh
typo

[Stubby]

5 minutes ago, richvdh said:

Hi folks, wanted to post a follow-up here.

 

Long story short, I rebuilt the saw and gave it its first proper workout this weekend and it worked beautifully!

 

Following the advice on this thread, I cleaned up the cylinder as best I could with NaOH, then a bit of wet & dry, and finally a cylinder hone; and I fitted a new piston and ring. To do a pressure test, I struggled to get a seal on the intake with homemade plates: it's a funky shape with several different channels. In the end I just spent £10 on the Husqvarna service tool and connected the pressure tester to the spark plug tool.

 

Compression and pressure tests were both good so I fed it some Aspen Alkylate fuel and it seemed to be running happily, so at the weekend I took it out to the wood and used it for a couple of hours with no problems at all.

 

It's a lovely saw when it's working right! Thanks to everyone who offered advice here to help me salvage it.

Thanks for the update . Glad its fixed . 

[spudulike]

Yup, that inlet manifold is a bit of a sod when doing a pressure/vac test.