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Mick McD

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May 6, 2017
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Location
Manchester
Hi everyone,

I’ve been hanging around here a while soaking up all the knowledge you guys are kind enough to share but this is my first post. I’m sorry in advance if this post is a bit long but I just want to give as much information as possible in the hopes that someone can help me.

I bought a 560XPG a few weeks ago as a gift for my dad in Ireland (he needs a new saw and I thought the heated handles would be good for the arthritis in his hands). The saw was sold as having ‘an intermittent running problem’ (this from the guy that was selling it “plenty of compression, starts revs but then coughs and dies but then will start etc so selling as spares or repairs”).

I got the saw and when I checked the muffler it was slightly loose and when I removed it I could see some light scoring on the piston but it didn’t look too bad at all. I did a compression test at WOT and my gauge showed 60psi but I have since found out that this would not have been accurate as I replaced the Schrader valve in my tester a while back with one from a tyre not knowing that it should be a special lightly sprung one. Also I was using a 14mm to 10mm adapter so I know that this would have brought the reading down.

A pressure test and a vacuum test showed the saw was airtight and I tested the fuel lines and these were fine also so I got to work on the cylinder with acid and Scotchbrite and it seemed to me to clean up fairly well. There did seem to be some streaks on the cylinder walls but nothing I could catch my finger nails on but for two small vertical grooves by the right hand side of the exhaust port. I knew these would definitely have an impact on the compression but I have come across that in other two stokes I’ve rebuilt (including a 550XP I did last year) and they’ve always run fine for me. I put a Meteor piston with a Caber ring on in, got it back together and pressure and vacuum tested it again. I also did another compression test (not yet knowing at this point about having the wrong Schrader valve) and was confused that the reading I got was exactly the same, 60 PSI.

Anyway I went to fire it up and it performs exactly as it did before I did any work on it. When freshly rebuilt it’ll run (I presume because the excess oil in the cylinder from the rebuild is allowing a bit more compression) but bogs when the throttle is applied. After a few starts it’ll no longer run, just fire once then die. When the muffler is removed the cylinder seems to be very wet. In my limited experience this would all point toward low compression but without a working gauge at the moment I can’t be sure.

But what confusing me is that the saw doesn’t FEEL like it’s low…. It takes a good pull on the rope even with the decomp in and it’ll only drop very slowly if I lift it off the ground by the starter rope. The other thing is, the saw doesn’t look like it’s had a long hard life to the point that the cylinder could just be worn out (plastics all look bright and shiny etc.). The acid has no effect on any part of the cylinder when applied now so that leads me to believe that not only is any tramp aluminium from the piston gone but that the Nikasil is worn through either. Surely, a brand new piston and ring should’ve increased the compression enough for it t run at least.

Is there something I’m missing? Should I get back into the cylinder with some Scotchbrite and keep at it or is it toast?

I'll try and get some pictures of the cylinder up tonight but any advice anyone can give would be greatly appreciated as a new cylinder over here in the UK is over £300. Money I just don’t have to put into it but I’d love to get her going again!
 
It seems to be a coil/carb problem?
You tried with a new spark plug? Spark wire is good all the way from the coil to the spark plug?
I also have a Jonsered 2258/Husqvarna 555 and had the cylinder/piston scored, cleand them up with scotchbrite and it runs good now. I just put a new ring in it.
 
In my limited experience if it's got good compression maybe your carb was put together wrong (or need a rebuild) and flooding, had a 390 in here a while back and the guy I bought it off said he put a carb kit in it and he had the needle area in the wrong order, flooded like crazy after the rebuild, should have looked at that before I put it back together given his mechanical rep- maybe worth a look if you haven't already.
 
It seems to be a coil/carb problem?
You tried with a new spark plug? Spark wire is good all the way from the coil to the spark plug?
I also have a Jonsered 2258/Husqvarna 555 and had the cylinder/piston scored, cleand them up with scotchbrite and it runs good now. I just put a new ring in it.
Yes I've tried a new plug and the spark wire looks undamaged.... and the spark tester shows it's making a good spark.
 
In my limited experience if it's got good compression maybe your carb was put together wrong (or need a rebuild) and flooding, had a 390 in here a while back and the guy I bought it off said he put a carb kit in it and he had the needle area in the wrong order, flooded like crazy after the rebuild, should have looked at that before I put it back together given his mechanical rep- maybe worth a look if you haven't already.
Well as I say, I can't be sure it's got good compression without a tester but I think you're right, it's worth rebuilding the carb just to see if it helps. I've already had it apart to make sure nothing was blocked with dirt or anything; the needle looked fine and the metering lever seemed to be at the right height but as you say, someone might have had it apart and put the diaphragms and gaskets back in the wrong order.

One other carb related theory I had was this: the muffler bolts were slightly loose when I got it. Perhaps the saw had started to run lean when it was with it's previous owner because of this and the AT had compensated by richening up the mixture. But since the rebuild, there is now no air leaking in where it shouldn't so the mixture is too rich for the saw to run and therefore the AT can't recalibrate itself. I don't know if that theory makes sense but based on that line of reasoning I did bring it into the only Husqvarna dealer near me last week for them to hook it unto the computer and reset the software but the mechanic that I used to deal with there had left the company and the new guy had never even heard of a computer controlled carb (he thought the 560xp was a lawnmower!)!?!?
 
A factory reset is a good place to start. I would also go through the carb to make sure everything is right, like the metering diaphragm and gasket being reversed, or the metering lever being too high.

I did take it to the only Husky dealer anywhere near me for them to reset the car Andy but the mechanic I used to deal with there had moved on an the new guy had didn’t even know what AT was! He looked at me like I had two heads when I was trying to explain it to him. Anyway, all seems right inside the carb as far as I can see so I thought I’d do a rebuild but can’t find the kit listed on Zama’s site (it’s an EL48 carb). I know the EL44 kit was RB-181, does anyone know if it’s the same kit for the EL48 and if so if anyone sells it in the UK because I can’t find it anywhere!
 
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