Husqvarna 560: part seized?

[Sviatoslav Tulin]

17 hours ago, richvdh said:

@pleasant: thanks for the reply. I can totally see this from the dealer's point of view, and yes I'm sure "it's not been misfuelled" is a story they've heard a hundred times before.

 

But the thing is, I really am 100% sure that I've never misfuelled it, and if I did get it rebuilt, I don't know what I would do differently to stop it happening again.

 

> in fact he will lose more by informing of this, as you probably won't have the repair done

 

Well... he might not be that wild about taking up the argument with Husqvarna; it's not exactly going to be a money-spinner for him. But still, I take your point, he's not saying this without good reason.

 

Is there anything else that could cause similar symptoms to under-oiling? A fault in the electronic mixture control leading to a lean air/fuel mix, maybe? In short, anything specific I should ask him to check?

 

Even knowing if it's something I've done wrong in the mix prep would at least put my mind at rest. I've always just got a 5L can of unleaded, dumped in 100ml of Stihl HP using the measure on the bottle, and then given it a good shake before pouring it into the saw. Maybe 1:50 is a bit of a lean mix, though it's what the manual says to use.

 

I guess it's possible the mixed fuel had been sitting in the can/saw for a couple of months, could that have caused the problem?

 

Absolutely.

[ChrisNewport]

If its nice and shiney with the paint still on the bar, stick it on ebay as spares or repair when they have a cheap listings weekend and with the proceeds youll have enough to buy yourself a brand new one and have enough left over for a week in the sun. People are paying crazy money for knackered gear on there at the moment. I wish id not cleared out all my scrap 2 years ago. Could have got twice as much for it today.

[Fatboy2017]

Another thing you can do to satisfy yourself is to have a look at the fuel, I suppose you still have some? Tip it into a glass container from the can or whatever you keep it in, do not shake it, just dispense it and leave it a while, check the colour first and you could see water separating out and fuel goes cloudy as it goes off, plus smell it, stale fuel smells!  If you cannot see anything obvious you can get it tested, but it costs of course!

This may help with your self doubt or confirm it's the fuel or not.

 

[richvdh]

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?

 

[Dan Maynard]

Definitely worth a go cleaning up the cylinder, anyway it's cheap to try and there's a good chance it is ok underneath the layer of aluminium that's come off the piston.

 

Exhaust side will pick first as hotter, and less oil. Once the aluminium transfer starts then it increases friction so gets even hotter.

[openspaceman]

1 hour ago, Dan Maynard said:

Definitely worth a go cleaning up the cylinder, anyway it's cheap to try and there's a good chance it is ok underneath the layer of aluminium that's come off the piston.

 

Exhaust side will pick first as hotter, and less oil. Once the aluminium transfer starts then it increases friction so gets even hotter.

Yes and the aluminium pick up will need chemically removing.

 

It looks messy but as the ring hasn't smeared over with aluminium I'd say it was no a bad seize however the piston and ring are toast.

 

The light colouring on the exhaust port and piston crown suggest to me the fuel to air mixture was a bit weak (lean), I am not sure how that can happen where the fuel is adjusted electronically.

[spudulike]

The fella admitted to using fuel mix at least two months since mixing, perhaps longer so there's your route cause.

The cylinder looks like it may well clean up. Chemically remove the transfer and then either lightly hone or rub with wet and dry and fit a new OEM, Meteor or Hyway piston.

[openspaceman]

If it were that critical I would seize one every outing  when in fact I have only seized a 268 back in the days of four star when I picked up the wrong can.  I think only red metal cans were legal then.

 

Trying to teach young ladies to  hear the engine note and not cut at part throttle is a difficult job which I failed on but lack of mechanical sympathy is what contributes to most problems. Back in the day it was blokes tweaking the HI screw to get more revs and not realising it reduced cutting power that was the problem. Presumably less so with modern saws.

[waterbuoy]

Did you mean ladies or laddies - or even both?

[openspaceman]

37 minutes ago, waterbuoy said:

Did you mean ladies or laddies - or even both?

Because I am old and non pc I meant what I wrote. Up till recently I worked on a gang with two or three young ladies and they were excellent in most things except the sound and feel of a motor saw cutting correctly. This is just my observation as there are plenty of mechanically sympathetic women out there,