I have an 026 Pro that I am curious about the compression on. I have a "good" screw-in gage to check it with but wonder the correct way to check it. Should the saw be cold or up the operating temp? Should I hold the throttle wide open or not? What should the compression be on this saw? I am new to all this and need help/suggestions. Thanks.
What should compression on 026 Stihl be?
- Thread starter BIG
- Start date
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I do not know what the comp spec is for that model, but the standard procedure for a comp check is throttle wide open while engine is still hot.
try cold and warm
Hi,
so far i know:
Choke in, full thotle,pull stong.
Compare the Test in Cold and in warm. When the piston is warm, compression is better because it is bigger.
You could still have starting/compression problems because of low compression in cold.
Camel
Hi,
so far i know:
Choke in, full thotle,pull stong.
Compare the Test in Cold and in warm. When the piston is warm, compression is better because it is bigger.
You could still have starting/compression problems because of low compression in cold.
Camel
If the hot comp is good the cold will be also. Hot is really the only one that matters as a engine quickly heats during use.
@bwalker
@ walker
Hmmmm.....I had a 026, had good compression when warm, terrible strart-Problems because of bad Rings when cold.
New Rings leads to good Comp in cold and warm(in my case)...
So far im my 026...must not be in every saw.
Camel
@ walker
Hmmmm.....I had a 026, had good compression when warm, terrible strart-Problems because of bad Rings when cold.
New Rings leads to good Comp in cold and warm(in my case)...
So far im my 026...must not be in every saw.
Camel
compression
Grab starter handle and pick up saw with it. Rope shpuld not pull out of saw or come out VERY slowly. I have never seen any specs for compression pressure on a Stihl, this is the way I check all my saws. Has not failed yet.
Grab starter handle and pick up saw with it. Rope shpuld not pull out of saw or come out VERY slowly. I have never seen any specs for compression pressure on a Stihl, this is the way I check all my saws. Has not failed yet.
Tony Snyder
Addicted to ArboristSite
Compression is just high enough to make the standard factory rope break after about 100 starts.
This surprises me
I am a beginner with chainsaws but I have worked on cars and equipment all my life. It really surprises me that Stihl doesn't publish acceptable compression values for Stihl saws. Seems so crude to assume compression is good enough by picking up the saw by it's rope and seeing if the rope comes out. I mean, if you compare 2 saws and both pass this "rope test" equally, one still may have considerably better compression than the other. You can never tell by this method. I am so used to sticking a gage in each cylinder of larger 4-stroke engines that I guess I am ruined. Surely a bunch of you experienced chainsaw folks have some idea of compression numbers on saws you have rebuilt in the past?
I am a beginner with chainsaws but I have worked on cars and equipment all my life. It really surprises me that Stihl doesn't publish acceptable compression values for Stihl saws. Seems so crude to assume compression is good enough by picking up the saw by it's rope and seeing if the rope comes out. I mean, if you compare 2 saws and both pass this "rope test" equally, one still may have considerably better compression than the other. You can never tell by this method. I am so used to sticking a gage in each cylinder of larger 4-stroke engines that I guess I am ruined. Surely a bunch of you experienced chainsaw folks have some idea of compression numbers on saws you have rebuilt in the past?
Stumper
One Man Band
Perhaps no compression specs is a German thing. I don't know about now but in the past Porsche did not publish compression specs -only reccommended specs about % of compression differential between cylinders. There is a logic to that-if the engine runs well with 90Lbs across all cylinders why have people worried about getting a 110 lb average(or whatever). Stihl probably avoids having customers scream about low compression by not publishing specs.
Stumper, maybe you are right
It sounds like there is some logic to what you say but, in my opinion, this is a lousy way for a manufacturer to look at things. Compression on an engine tells a very important story. Anyway, I checked my 026 Pro and I get compression readings as follows:
1st pull - 70psi
2nd pull - 110 psi
3rd pull - 125 psi
This was checked with the motor warm, throttle wide open and choke open. I made each pull of the rope very fast and strong with a full length pull of the rope. These numbers were obtained in two different back-to-back tests. Are these numbers similar to what some of you have seen? I just don't have anything to compare it to.
It sounds like there is some logic to what you say but, in my opinion, this is a lousy way for a manufacturer to look at things. Compression on an engine tells a very important story. Anyway, I checked my 026 Pro and I get compression readings as follows:
1st pull - 70psi
2nd pull - 110 psi
3rd pull - 125 psi
This was checked with the motor warm, throttle wide open and choke open. I made each pull of the rope very fast and strong with a full length pull of the rope. These numbers were obtained in two different back-to-back tests. Are these numbers similar to what some of you have seen? I just don't have anything to compare it to.
Compression on a 4 stroke is a diagnostic tool that accounts for the valve train, head gaskets, etc. The 2 stroke doesn't have those items. If it won't run and the starter rope pulls easy, it's rings/cylinder wall.
Ryan Willock
Addicted to ArboristSite
Tony, i have well over 100 starts on my 036's ,021, my old 026 before i sold it and have never had a rope break from that few starts. i have had a rope break before but its rare, i think that it is more of a defect with the rope or how you take care of your saws. if you get a lot of dirt down on the rope and don't clean it then i can see where that would be a problem as the dirt would be highly abrasive:angel:
Point taken WRW, but...
True enough, for 4-stroke engines, a compression test is a tool that tells a story about a much more complicated valve train that 2-strokes don't have. But, there is undoubtedly varying degrees of wear in all of the 2-stroke equipment out there and the rope pull test just tells you "good" or "bad". What about the engines that happen to just barely pass your rope pull test but have significant wear and will only last a few more hours before they fail it? With compression numbers as guidlines you are able to foresee such a problem before it bites you.
True enough, for 4-stroke engines, a compression test is a tool that tells a story about a much more complicated valve train that 2-strokes don't have. But, there is undoubtedly varying degrees of wear in all of the 2-stroke equipment out there and the rope pull test just tells you "good" or "bad". What about the engines that happen to just barely pass your rope pull test but have significant wear and will only last a few more hours before they fail it? With compression numbers as guidlines you are able to foresee such a problem before it bites you.
jokers
Addicted to ArboristSite
Hi Big, don`t mean to alarm you, but from what I have seen you are slightly on the low end of the scale of good compression for a saw. All of the saws that at I have tested that are running near peak are atleast 140# psig, normally higher. I`m sure it took a long time to get where you`re at now so failure is probably not imminent, but on the other hand, a ring job is cheap when everything else is good. Maybe some of the motocross motorheads can help out, but from what I have been told by a friend who is a motocross and race sled engine builder, 100# will not even run. There again, doesn`t mean the engine is toast, just time for a teardown. Russ
Checked comp. on a new engine to compare
Folks, all this wondering about whether the compression #'s on my 026 were acceptable is getting to me. Therefore I decided to check the compression in a nearly new (less than 5 tanks of fuel) Echo PB-2100 blower I have. I bought it new, it still runs as new. I used the same compression gage that I used on my 026 and got the following numbers:
-1st pull - 80psi
-2nd pull - 105psi
-3rd pull - 110psi
-4th pull- 110psi
-5th pull - 110psi
I did this with the engine stone cold and hot and saw no difference. These numbers tend to show my 026's numbers (listed in previous post) are fine but I looked back on some old threads and some of you say a saw in good shape should be 140-150psi - what gives?
Folks, all this wondering about whether the compression #'s on my 026 were acceptable is getting to me. Therefore I decided to check the compression in a nearly new (less than 5 tanks of fuel) Echo PB-2100 blower I have. I bought it new, it still runs as new. I used the same compression gage that I used on my 026 and got the following numbers:
-1st pull - 80psi
-2nd pull - 105psi
-3rd pull - 110psi
-4th pull- 110psi
-5th pull - 110psi
I did this with the engine stone cold and hot and saw no difference. These numbers tend to show my 026's numbers (listed in previous post) are fine but I looked back on some old threads and some of you say a saw in good shape should be 140-150psi - what gives?
treeclimber165
Member A.K.A Skwerl
Two things I can think of on your blower, BIG. It isn't fully broken in yet, so you can probably expect closer to 125-130 lbs with another 5-6 tanks of fuel. Second, blowers (especially lil ones like the 2100) are not built for high performance. Reliability is more important that horsepower with a blower. It's not like you are really torquing the motor when you bear down on a pile of leaves.
Tony- I've observed that the people who break starter ropes are the people who like to hold a saw by the rear handle with a finger on the throttle when starting it. By pulling the rope handle back, the rope is bent at a 90* angle and drug across the side of the opening. This will trash a starter rope after 100 pulls or so. By setting the throttle lock, holding the saw by the top handle and pulling the rope straight up, you are not needlessly abusing the rope and it will last for the life of the saw.
Tony- I've observed that the people who break starter ropes are the people who like to hold a saw by the rear handle with a finger on the throttle when starting it. By pulling the rope handle back, the rope is bent at a 90* angle and drug across the side of the opening. This will trash a starter rope after 100 pulls or so. By setting the throttle lock, holding the saw by the top handle and pulling the rope straight up, you are not needlessly abusing the rope and it will last for the life of the saw.
Ryan Willock
Addicted to ArboristSite
good point brian, i just about always start my saws in that manner (drop starting) it is also hard on your wrists to start them by holding the rear handle. i can see where it is entirely possible to break or sprain your wrist by dropping the saw while holding only the rear handle
especially if the motor locks up.
just my thoughts on the subject:angel:
especially if the motor locks up. just my thoughts on the subject:angel:
NevadaWalrus
ArboristSite Operative
Stihl DOES list compression figures and it is an improtant diagnostic tool. Where all 2 cycle manufacturers really screw up is by not making a provision for checking crankcase pressure and the proper specs. This is every bit as important, if not more so, then combustion chamber compression on a 2 cycle.
I'll check today to see if my list has the 026 on it, my spec chart is getting old.
I'll check today to see if my list has the 026 on it, my spec chart is getting old.
NevadaWalrus
ArboristSite Operative
OK, here goes. First, forget about 1st, 2nd, 3rd or whatever the number of pulls are. Pull the starter until the guage no longer climbs. This is particularly important if you're using a large guage and hose really made for automotive uses. It simply takes a while to fill the guage and hose up to pressure.
Reading are for cold. Why? If diagnosing a dead engine you CAN'T warm it up. A warm saw shouldn't be more then 5% different either way.
New saw, not yet broken in should have between 115 and 125 psi. One broken in should read 125 to 130 psi. Also, reading will be about 5 psi lower for every 1000' elevation above sea level.
Reading are for cold. Why? If diagnosing a dead engine you CAN'T warm it up. A warm saw shouldn't be more then 5% different either way.
New saw, not yet broken in should have between 115 and 125 psi. One broken in should read 125 to 130 psi. Also, reading will be about 5 psi lower for every 1000' elevation above sea level.
Thanks Nevadawalrus - I knew comp. #'s are important
Thanks for looking the comp. spec up for me. Looks like my 026 is in good shape just after a rebuild hitting 125psi. I posted that it took 3 pulls because after 3 pulls it no longer climbs anymore. My stepfather has a Husky 55 Rancher that he bought new and it has only had 5-7 tanks of fuel through it - it took it 3 pulls to reach 130psi and it wouldn't climb any higher. I feel good about my 026 with 125psi and fresh rings. I know if that 55 is only 130 and it is nearly out of the box new, and has been taken care of, my 125psi is right on the money. By the way, I am using a large automotive type gage that does have a large hose capacity (thus 3 pulls to get accurate readings) and I am barely above sea level.
Thanks for looking the comp. spec up for me. Looks like my 026 is in good shape just after a rebuild hitting 125psi. I posted that it took 3 pulls because after 3 pulls it no longer climbs anymore. My stepfather has a Husky 55 Rancher that he bought new and it has only had 5-7 tanks of fuel through it - it took it 3 pulls to reach 130psi and it wouldn't climb any higher. I feel good about my 026 with 125psi and fresh rings. I know if that 55 is only 130 and it is nearly out of the box new, and has been taken care of, my 125psi is right on the money. By the way, I am using a large automotive type gage that does have a large hose capacity (thus 3 pulls to get accurate readings) and I am barely above sea level.
