When to replace the cylinder

[mifirewoodguy]

I have a few saws that have been leaned out for one reason or another, a cpl of the cylinders are borderline for what I might concider replacement. What I would like to know from you guys is what are your determining factors when deciding if a cylinder has had it? I have a husky 350 and a 55 that have some very small straight scrathes that wont hone out, both are almost top to bottom accross the exhaust ports. When running my finger over them their barely detectable but visable to the naked eye. When should you decide to scrap these types of damaged cylinders? Others I have honed have came out clean with no visable metal residue or scratches. Thanks.. Lee..

 

[Brmorgan]

I have a few saws that have been leaned out for one reason or another, a cpl of the cylinders are borderline for what I might concider replacement. What I would like to know from you guys is what are your determining factors when deciding if a cylinder has had it? I have a husky 350 and a 55 that have some very small straight scrathes that wont hone out, both are almost top to bottom accross the exhaust ports. When running my finger over them their barely detectable but visable to the naked eye. When should you decide to scrap these types of damaged cylinders? Others I have honed have came out clean with no visable metal residue or scratches. Thanks.. Lee..

From your description they don't sound like a writeoff yet. What kind of shape are the pistons in? I think the only way to know for sure is to throw a new set of rings on the pistons, run a tank thru to allow them to seat properly, and then get out the compression tester. If you're still getting good compression, then I wouldn't worry about them. I have an older Husky 50 that tests out at 138 PSI which isn't spectacular, but the saw still screams, idles perfect (after a carb rebuild) and cuts like a hot knife thru butter. Cylinder has some minor marks which were there when I got it from the pawnshop, and the saw could probably do well to have the rings replaced as the piston does not have the same marks as the cylinder. I'd have to see pictures of yours to know how it would compare though.

 

[mifirewoodguy]

Thanks Br,
Most of the pistons are junk from being leaned out(straight gassed) and wearing on the exhaust side of the cylinder, The scratches I mention are from that reason. Just wondering how bad/deep the scratches have to be before their junk. I planned on putting new piston/rings in em but dont want to waste my time rebuilding a saw that needs a new cylinder....Thanks Lee

 

[Brmorgan]

I had the same problem with my Poulan 2150 (!) when I found it in the scrap bin of a local store. Piston was toasted, and the cylinder was scored pretty good. I picked up a new piston kit for pretty cheap and threw that in. While it RUNS, it isn't very usable - the compression is low to the point that I can either tune the carb so that the saw starts really well, or so that it runs really well, but so far the two are mutually exclusive. I never have put the compression tester on it yet though so I don't have any real numbers on it for reference, nor have I spent any time working on it in the last couple years since my saw knowledge and experience have really grown a lot. I should try to find a hone to fit it and maybe that would improve it a bit, as it would make a really good little saw to throw on a backpack to do trail building or clearing.

I don't have enough experience to give any definitive point where a cylinder should be scrapped - I'm sure there are fanatics out there who would say that as soon as compression starts to go down it's time to rebuild, and then there would be others who would say as long as it starts and runs it's good to go. In this case I'd say to start with a new piston and rings, and see if you're happy with the results. If the saw runs OK and cuts to your satisfaction, no sense replacing the cylinder.