Mick McD
New Member
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!
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!
