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Author Topic: Low compression?  (Read 741 times)

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Offline 421Altered

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Low compression?
« on: November 07, 2019, 09:47:35 PM »
I have a stihl 032 that I bought new in 1985, and a 024, that I bought new about 1990, not exactly sure as I didn't write it down in my owner's manual.  I tested both of them with my new Horrible Freight tester, and the 024 has 32psi, the 032 has 41psi.  They both run good, and I keep the chains sharp, and saws tuned up.  My question is how much would it cost to rebuild these saws and are parts still available for them?  I want to keep them as they have sentimental value to me.

Offline sawguy21

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Re: Low compression?
« Reply #1 on: November 07, 2019, 11:16:02 PM »
Something wrong with the tester, they shouldn't fire with those numbers. :o I don't use one on two strokes, I pull the muffler and have a look at the piston and rings.
old age and treachery will always overcome youth and enthusiasm

Offline Al_Smith

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Re: Low compression?
« Reply #2 on: November 08, 2019, 05:16:18 PM »
If they run okay I wouldn't be concerned .

Offline ZeroJunk

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Re: Low compression?
« Reply #3 on: November 08, 2019, 05:18:26 PM »
Especially if they will just sit and idle when tuned correctly.  Might want to get the tester rebuilt.

Offline Al_Smith

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Re: Low compression?
« Reply #4 on: November 08, 2019, 07:30:33 PM »
You have to keep in mind who sold the tester .

Offline 421Altered

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Re: Low compression?
« Reply #5 on: November 08, 2019, 09:20:28 PM »
Thanks guys.  I feel much better about them now.  They will sit and idle all day once they get to operating temp.  It must be the cheap tester.  These saws are the only things I've used it on so far.  Thanks again.

Offline 421Altered

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Re: Low compression?
« Reply #6 on: November 09, 2019, 07:04:04 PM »
Sawguy,  Exactly what are you looking for when you look at the piston and rings.  I'm familiar with 4 stroke racing engines on alky, so, I know what those should look like, but, with the oil mix, and gasoline, there is so much soot/carbon that I don't know how to read these engines.  Thanks.

Offline ZeroJunk

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Re: Low compression?
« Reply #7 on: November 09, 2019, 09:24:41 PM »
It is difficult to find a compression gauge that will accurately read the compression of a very small displacement engine started by hand. Mine will read fine on a PWC for instance, but a 30 cc weed eater you can pretty much for get it.

If you can find one with a very short hose, and the valve has to be in the  spark plug fitting end of the hose. Plus it has to be a low pressure valve, a regular tire valve will not work.

I never saw the point in spending a lot of money on a Snap On or something when how the engine runs tells you what you need to know.

If you want to look for a problem I'm sure you can find one.

Offline sawguy21

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Re: Low compression?
« Reply #8 on: November 10, 2019, 12:40:45 AM »
Sawguy,  Exactly what are you looking for when you look at the piston and rings.  I'm familiar with 4 stroke racing engines on alky, so, I know what those should look like, but, with the oil mix, and gasoline, there is so much soot/carbon that I don't know how to read these engines.  Thanks.
I look for scoring or galling and carbon buildup on the piston skirt as well as excesively worn/broken rings. Rings sloppy in the piston groove indicates wear often the result of poor air filter maintenance.
old age and treachery will always overcome youth and enthusiasm

Offline ehp

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Re: Low compression?
« Reply #9 on: November 10, 2019, 09:45:41 AM »
its the tester , I have seen warranty chainsaw shop places not even think why they are getting such lower numbers , common one these days is they use a tester that was meant for the bigger sparkplugs and just screw a adaptor that fits the smaller spark plugs a lot of saws now a days have . But they for get that they now also have the volume of the adaptor so that lowers the numbers huge

Offline 421Altered

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Re: Low compression?
« Reply #10 on: November 10, 2019, 12:32:49 PM »
Wow!  Thanks for all of that good info from all three of you!!  ZeroJunk, SawGuy, and EHP, that info means a lot to me.  Like I said, I'm familiar with V8 racing engines on alky, but, these very small 2 stroke engines on gas/oil are another story.  Many thanks!!

Offline Al_Smith

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Re: Low compression?
« Reply #11 on: November 10, 2019, 02:33:40 PM »
An old test without a comp tester .Grab the start handle and drop the saw .The compression should hold it up .

Offline 421Altered

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Re: Low compression?
« Reply #12 on: November 10, 2019, 09:34:27 PM »
Thanks Al!!  Unfortunately all of my saws flunk this test!! They just slowly unwind the starter rope in steps!!  They still run, but, I know they need rebuilding.

Offline Al_Smith

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Re: Low compression?
« Reply #13 on: November 11, 2019, 06:52:35 AM »
A lot of times just a tug on the starter tells the tale .I've got a Partner P100 that pulls over rather easy .Now that is 99 cc with no decomp,shouldn't  be easy .It runs,cuts but certainly not like 99 cc should by any means .By the same token I have a Husqvarna 2100 CD I had to install a D-handle because of the compression,same displacement as the previously mentioned saw .BTW it does cut good .

Offline ZeroJunk

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Re: Low compression?
« Reply #14 on: November 11, 2019, 07:21:35 PM »
Thanks Al!!  Unfortunately all of my saws flunk this test!! They just slowly unwind the starter rope in steps!!  They still run, but, I know they need rebuilding.
I think I would go to a dealer and try that with a new saw before you make a big deal out of it.

Offline 421Altered

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Re: Low compression?
« Reply #15 on: November 12, 2019, 03:06:38 PM »
Zero,  I don't know what you are talking about me making a big deal out of it?  What do you mean?  

Offline lxskllr

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Re: Low compression?
« Reply #16 on: November 12, 2019, 04:07:52 PM »
I think he's saying you might find new saws can't hold themselves up either, so don't get excited about it. I don't have extensive experience, but all my saws will hold themselves up. My PoulanPro /may/ be an exception, but it has some kind of "easy pull" system on it. I should look it up to see how it works. It's definitely easy to pull, but it doesn't feel like there's anything at the end of the cord. Not sure I like it, especially on a 42cc saw. They aren't hard to pull over anyway.

Offline Al_Smith

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Re: Low compression?
« Reply #17 on: November 12, 2019, 05:43:17 PM »
A set of Caber piston rings for either saw would be around 12-15 dollars .That should fix the problem 

Offline ZeroJunk

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Re: Low compression?
« Reply #18 on: November 12, 2019, 05:48:29 PM »
I think he's saying you might find new saws can't hold themselves up either, so don't get excited about it.



Yeah. It's not an exact science. I think if you find a saw that will hang there forever then it is probably locked up. LOL.  Or, dry as a bone from not being used.

Offline Al_Smith

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Re: Low compression?
« Reply #19 on: November 12, 2019, 06:58:24 PM »
I might have one or two that would drop but on the other hand I'd lay a good wager even the heavy ones,like a 084 Stihl will hold .It's dark as the inside of a  boot and cold as a well drillers behind out so I'll check it out tomorrow .I wish this Siberian express would go back to where it came from--brrr----


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