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.

> 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.

> 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.

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?

Interesting. Do the premixed fuels keep ok?

Well, that all seems very clear, thanks for the explanation @spudulike. Today I learnt an expensive lesson. I guess now I need to figure out what to do with my saw. I can't see any point in spending 90% of a new saw in rebuilding it...

Yes, the red, standard, HP. And standard unleaded from a supermarket. Given the manual says max 10% ethanol, I kinda believed it... I had no idea these things were so sensitive. I've had other saws which have run fine for years... Sigh, it's sounding like that might be a factor. And as @pleasant says, honestly it's probably more than 2 months really. It takes me a while to get through a 5L can. Is the problem storing it mixed, or storing it at all? Would a fuel conditioner help?

Hmph. If it needs Husqvarna XP to stop it blowing up, that needs making clear in big red letters. I didn't get any advice from the dealer when I bought mine, but the manual says "For best results and performance use Husqvarna two-stroke oil. If Husqvarna two-stroke oil is not available, use a two-stroke oil of good quality for air-cooled engines". That's a long way from "it must be XP".

@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?

I have a Husqvarna 560 which I bought brand new a few months ago. I've only used it a handful of times, and on the last couple it's started up fine but then stalled after a few minutes of work. I took it back to the dealer, who tells me it's been misfuelled, it is part seized, and will need a new piston and cylinder, for very nearly the price of the new saw, none of which will be covered under warranty. I am, frankly, livid. It's never been run on anything other than properly-mixed fuel using Stihl HP oil. Any advice on how I should proceed?