Just for the record, my step-father has a Husky 55 with less than 10 tanks of fuel through it - I got curious as to what it's compression was. I used the same automotive compression gage I used to test my 026. After 3 pulls the Husky 55 leveled out at 130psi. Makes me feel good since my 026 with fresh rings/piston got to 125psi in 3 pulls. After searching this forum on the "compression" subject, many have posted that a "good" saw should be at least 140-150psi. I just don't see it. I have tested every piece of 2-stroke equipment I have (and my family has) and the highest reading I saw was in this Husky 55 @ 130psi. Now, it is a possibility that my gage isn't exactly accurate. But it is a good Sunpro gage that has seen minimal use - seems like it should be right on. See previous post on 026 Compression if interested in more of the same.
Can't let this compression issue die
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John in MA
Addicted to ArboristSite
I tested my 111S with a Snap-On push gauge and it got around 120 after a few pulls. However, only the top ring is new in that saw.
dbabcock
Hi Tech Redneck
Two strokes are usually difficult to accurately gauge compression. Port timing is a major player in modifying the computed compression ratio (cylinder swept volume versus combustion chamber volume at the top of the stroke) into the so-called "effective" compression ratio (which is essentially what you get when you use a compression gauge to measure it at a low cranking RPM). The reason for this is that ports in the cylinder wall are opening and closing at different points in the stroke. Different porting for different two stroke engines will affect what you read on the gauge. The only way to get a good feel for this on a single cylinder two stroke engine is to compare it to other engines that are exactly the same model. On multi-cylinder two strokes such as outboard motors, it's usually said that the difference between the compression readings of any of the cylinders is more important than the absolute number.
eyolf
Addicted to ArboristSite
Don't feel bad. I've got a K-D tools gage that reads low, too. I think you've done the right thing to compare a few different engines so as to establish a baseline. I usually check the compression a couple of times a year, or when I think I may have a problem. When compression shows less than about 110, I consider myself to have a problem.
My brand-new chainsaws all showed about 130 or thereabouts. I do have a low-hrs Homie S-EZ that will pump up to 155.
My brand-new chainsaws all showed about 130 or thereabouts. I do have a low-hrs Homie S-EZ that will pump up to 155.
tony marks
Addicted to ArboristSite
ok . not to be cute. but in absense of these test tools, a sharp chain and a hunk o hardwood will tell me how strong she is. course it helps i u got some others to test it against.
would like to know what these power tuned saws create tho.
would like to know what these power tuned saws create tho.
Tony Snyder
Addicted to ArboristSite
Doug made the point well. It would be difficult to get a real meaningfull comparison between to saws that have porting designed differently; one saw may have a very good dynamic compression, in other words at running speed, but show low cranking speed compression because of port timimg subtleties, but yet be a very healthy normal saw.
Put in other words; it works like it is supposed to at speed, but not so well at cranking.
Also, are not those longitudinal thin slots you some times see, in effect, a built in compression release that more or less disappears at speed?
Old BSME, physics major, heat, light, sound, and fluid dynamics. Forgot most, but sometimes remember just enough to get me in trouble.
Put in other words; it works like it is supposed to at speed, but not so well at cranking.
Also, are not those longitudinal thin slots you some times see, in effect, a built in compression release that more or less disappears at speed?
Old BSME, physics major, heat, light, sound, and fluid dynamics. Forgot most, but sometimes remember just enough to get me in trouble.
Acer
ArboristSite Operative
Sort of related to compression, my 026 packed up last Feb, took it to a dealer who fitted a new piston. He told me there had been a fair bit of carbon built up around the exhaust port. After reading some of these posts, I was a bit disappointed to find i could still pull the starter cord out without any danger of lifting the saw off the ground...but it worked, so I carried on.
Anyway, I took the exhaust off this weekend to see what the carbon situation was, and found that there are no rings fitted to the piston. Is there any reason why the dealer would not fit new rings with the new piston? Is there any reason why I shouldn't blast him on Monday morning when his shop opens?
Anyway, I took the exhaust off this weekend to see what the carbon situation was, and found that there are no rings fitted to the piston. Is there any reason why the dealer would not fit new rings with the new piston? Is there any reason why I shouldn't blast him on Monday morning when his shop opens?
Robert
ArboristSite Lurker
I checked the compression on my old 090 a couple of weeks ago and it was 150 cold. I used an automotive gauge and pulled about 4 or 5 times to make sure the neelde had stopped moving.
tony marks
Addicted to ArboristSite
take it easy acer. mabe hes getting old like me,an just forgot
. in any case id sure letim know about it. surprised it cut good like that..
. in any case id sure letim know about it. surprised it cut good like that..
Acer, was the saw "noisey" upon intial start up? I would believe that it would be until the piston has expanded enough to get a tigher fit.
I am suprised that it ran at all. I have heard of some high tech formula 1 engines running without rings to reduce friction and increase power.
Anyway, keep us posted on to what the dealer tells you. Should be a good story
Good luck!
I am suprised that it ran at all. I have heard of some high tech formula 1 engines running without rings to reduce friction and increase power.
Anyway, keep us posted on to what the dealer tells you. Should be a good story
Good luck!
NevadaWalrus
ArboristSite Operative
Blast him Acer. Thats something that can't be forgot, don't mean shouldn't, it can't. Either it was on purpose or he has a really dumb, un-supervised beginer working on things.
Everyone, try this out if you get the chance. New piston and cylinder from a quality engine. I know it works with Echo. Turn the cylinder upside down, drop the piston in with no ring(s). Put thumb or finger over the plug hole and turn the cylinder right side up. The piston will stay put until you un-cover the plug hole.
Granted, the piston doesn't weigh much and air will pass by if you pull it out, but it will seal well enough to run, albeit not at full power.
Everyone, try this out if you get the chance. New piston and cylinder from a quality engine. I know it works with Echo. Turn the cylinder upside down, drop the piston in with no ring(s). Put thumb or finger over the plug hole and turn the cylinder right side up. The piston will stay put until you un-cover the plug hole.
Granted, the piston doesn't weigh much and air will pass by if you pull it out, but it will seal well enough to run, albeit not at full power.
Acer
ArboristSite Operative
I think it's going to be a blasting...The guy's not stupid, and knows his saws, but I smell a rat. The saw's 5 years old, hasn't had continuous use and has had proper maintenance. As soon as he saw it, he told me it was worn out, come to the end of it's life and he could give me a good price on a new Husky (he's a Husky dealer). How can it be worn out after 5 years? It's a STIHL !!
Anyway, it will be interesting to see what he says. It doesn't surprise me, because all the dealers round here are rubbish. They do the chainsaw thing as just another sideline, and you get the impression that it's them that's doing you the favour..they're mainly after tractor and big equipment sales and service.
I'm tempted to buy the rings and fit them myself, just for the experience. I've never done the job, or even fully stripped a saw down, and I'd be worried about screwing my one and only saw up, but if you don't try, you never learn. I used to think that it's best to stick to earning money tree cutting, and let the chainsaw "experts" do the work on the saws (they're supposed to have the tools and the know how). Now I'm not so sure.
Anyway, it will be interesting to see what he says. It doesn't surprise me, because all the dealers round here are rubbish. They do the chainsaw thing as just another sideline, and you get the impression that it's them that's doing you the favour..they're mainly after tractor and big equipment sales and service.
I'm tempted to buy the rings and fit them myself, just for the experience. I've never done the job, or even fully stripped a saw down, and I'd be worried about screwing my one and only saw up, but if you don't try, you never learn. I used to think that it's best to stick to earning money tree cutting, and let the chainsaw "experts" do the work on the saws (they're supposed to have the tools and the know how). Now I'm not so sure.
jokers
Addicted to ArboristSite
So what gives....
I had to go out and test a few saws after a typical 12 hour day, so I hope you guys appreciate it, lol, but my findings were consistent with what I said earlier. The saws are all in good running condition, various amounts of use. All tests were done with cold engines, WOT, and pulled until no more increase was noted, no more than 5. I used an Actron screw in gauge purchased at Autozone, and attempted to verify accuracy by rigging it to to regulated side of my shop compressor, was within two # at 125 psig. So here goes, Husky 345 - 152.5#, Stihl 019T - 160#, Husky 346Walkerized - 180#, Husky 357 Greffardized - 160#, and a like new Solo 647 - 152.5#. So my question is, where does anyone get the idea that 125 -130 psig is good for a broken in saw, or is that the threshold of ring time for a well used saw? Of course it is possible that my gauge is off, but what is the likelyhood that both the compressor gauge and the tester gauge are off? I can test more saws if necessary but it seems it would be academic. Russ
I had to go out and test a few saws after a typical 12 hour day, so I hope you guys appreciate it, lol, but my findings were consistent with what I said earlier. The saws are all in good running condition, various amounts of use. All tests were done with cold engines, WOT, and pulled until no more increase was noted, no more than 5. I used an Actron screw in gauge purchased at Autozone, and attempted to verify accuracy by rigging it to to regulated side of my shop compressor, was within two # at 125 psig. So here goes, Husky 345 - 152.5#, Stihl 019T - 160#, Husky 346Walkerized - 180#, Husky 357 Greffardized - 160#, and a like new Solo 647 - 152.5#. So my question is, where does anyone get the idea that 125 -130 psig is good for a broken in saw, or is that the threshold of ring time for a well used saw? Of course it is possible that my gauge is off, but what is the likelyhood that both the compressor gauge and the tester gauge are off? I can test more saws if necessary but it seems it would be academic. Russ
Tony Snyder
Addicted to ArboristSite
I'll try a couple tomorrow just for comparison. I also got a one ring 262xp out there with the ring almost stuck in its grove; I'll see what it does.
comp
OK my 2 cents again. You take all those readings and what do you really know? Not any more than I did when I picked it up by the handle. If it stayed up, it will have good compression. If it didn't, now I know I am going to start looking inside for for worn parts. I could have spent all that time with a guage and came up with the same results, but why? My time is better spent repairing the problem diagnosed as quickly as possible
OK my 2 cents again. You take all those readings and what do you really know? Not any more than I did when I picked it up by the handle. If it stayed up, it will have good compression. If it didn't, now I know I am going to start looking inside for for worn parts. I could have spent all that time with a guage and came up with the same results, but why? My time is better spent repairing the problem diagnosed as quickly as possible
jokers
Addicted to ArboristSite
Hi Stihltech, I agree with what you`re saying, I only checked some "field" numbers as a baseline to establish an opinion of what is normal compression IF measured. This thread isn`t really so much about what makes a saw run good as it is about numbers that someone came up with. By themselves the numbers mean nothing. Russ
Jokers findings are interesting
Jokers takes a logical approach to his compression testing by verifying the accuracy of his gage with his air compressor gage. Interesting... Very surprised to see all the saws he owns read 152psi or higher. ????, I have tested every piece of 2-stroke (good 2-stroke stuff) I have and a lot that my family and friends have and I haven't seen the first item get over 130psi. I know for a fact that several of these pieces of equipment are nearly new and are tuned right and have been taken care of. I am going out to run my 026 that started all this doubting in my mind in the first place.
Jokers takes a logical approach to his compression testing by verifying the accuracy of his gage with his air compressor gage. Interesting... Very surprised to see all the saws he owns read 152psi or higher. ????, I have tested every piece of 2-stroke (good 2-stroke stuff) I have and a lot that my family and friends have and I haven't seen the first item get over 130psi. I know for a fact that several of these pieces of equipment are nearly new and are tuned right and have been taken care of. I am going out to run my 026 that started all this doubting in my mind in the first place.
jokers
Addicted to ArboristSite
Hi Big, thanks for substantiating that my approach was at least logical. I tried taking pictures of the gauge with the pressures indicated but the artificial light kept reflecting off the lens, obscuring the pic. I tried mostly without flash. I figured this would be a hot potato type finding as soon as I saw the first reading last night, after reading the replies that stated that compression should(can) be lower. I can try sometime in the next week to get pics outdoors in natural light, and see if that makes them any clearer. It would be interesting if anyone else wanted to weigh in with their findings just for the sake of argument, or substantiation. Maybe both of my gauges are coincidentally off, the same amount in the same direction, but I would say it`s more likely that your numbers may increase with WOT run time, or maybe your gauge is reading low? I certainly wouldn`t worry about the numbers you are getting because your equipment is running good, and that is all we really want anyway. When I get a chance in the next few days I will test my Craftsman/Solo blower and see what the compression is just for kicks, blower motors are always lower initial compression though, LOL. Russ
NevadaWalrus
ArboristSite Operative
If the hang test works for you fine, I won't argue that it may be accurate most times. There are factors which may scew the hang test on some units though. An old saw from 20 years ago that weighs twice as much as a modern saw, or a modern saw with a much longer and heavier bar and chain installed then the norm. Recoil pulley size, a larger pully on a saw makes for easier starting--will also be more likely to drop on the hang test even when compression is good.
Also, I'm talking mostly about diagnosing a non running saw. One item that has to be checked is the spark plug so you're half way to doing a proper compression test anyway. We aren't talking about loosing much time are we. After all, sometimes we need to do a leak down test and that is where a lot of time is lost blocking off the ports. But sometimes it has to be done.
Besides, when the customer is contacted, he's going to feel a dang sight better about the diagnosis and your professionalism if you show him a compression number and what it should be instead of hearing you did a hang test. Telling him that his saw has "X lbs" or "X%" below minimum advised reading will go further then saying, "I picked it up by the rope grip and it fell to the ground.
Also, in the first thread I talked about crank case compression. Funny how no one around here ever talks about that. I've had many saws that felt like they had terrible compression based on rope pull but the guage told me otherwise. That tells me the piston skirt or crank seals are bad and there is little or no crankcase compression. So doing a proper guage test isn't a waste of time. Its part of doing proper diagnostics.
Also, I'm talking mostly about diagnosing a non running saw. One item that has to be checked is the spark plug so you're half way to doing a proper compression test anyway. We aren't talking about loosing much time are we. After all, sometimes we need to do a leak down test and that is where a lot of time is lost blocking off the ports. But sometimes it has to be done.
Besides, when the customer is contacted, he's going to feel a dang sight better about the diagnosis and your professionalism if you show him a compression number and what it should be instead of hearing you did a hang test. Telling him that his saw has "X lbs" or "X%" below minimum advised reading will go further then saying, "I picked it up by the rope grip and it fell to the ground.
Also, in the first thread I talked about crank case compression. Funny how no one around here ever talks about that. I've had many saws that felt like they had terrible compression based on rope pull but the guage told me otherwise. That tells me the piston skirt or crank seals are bad and there is little or no crankcase compression. So doing a proper guage test isn't a waste of time. Its part of doing proper diagnostics.
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