MS 250 Compression - What To Expect

[apn73]

Hello All,

Going to look at a used Stihl MS 250 tomorrow and was planning on taking a compression tester with me. How much compression can I expect on one of these saws that is in good health? What is the threshold that would suggest that something is wrong? Throw out any other used saw shopping tips that you can think of, can use the help.

Thank you advance,

Adam.

 

[moody]

Never had one on a gauge but by feel I'd say a used one should blow 145ish

 

[Wood Doctor]

Maybe I Can Help

Hello All,

Going to look at a used Stihl MS 250 tomorrow and was planning on taking a compression tester with me. How much compression can I expect on one of these saws that is in good health? What is the threshold that would suggest that something is wrong? Throw out any other used saw shopping tips that you can think of, can use the help.

Thank you advance,

Adam.

Well, Adam, I have a 10-year-old Stihl 025 in my shop right now that needs a new fuel line (hose). Looks like it has about 500 hours on it, but it's hard to tell. The original bar is in use but almost shot. Compression seems good, and I just bought a new compression tester to compare against my old one that could be a bit rusty. Saw starts and almost runs nicely, but the original fuel line has a few pinholes that are causing idling problems.

Would you like to know the results of a few comp tests on this engine?

 

[BloodOnTheIce]

Hello All,

Going to look at a used Stihl MS 250 tomorrow and was planning on taking a compression tester with me. How much compression can I expect on one of these saws that is in good health? What is the threshold that would suggest that something is wrong? Throw out any other used saw shopping tips that you can think of, can use the help.

Thank you advance,

Adam.

They run in the 135-145 range, pull the filter cover and check if the filter is properly seated.
If its loose pull filter and check if there's crud in the intake, and check the fuel line for cracks also.
These saws are really tough, not much goes bad if they're taken decent care of.

 

[lambs]

I'd like to see 150 psi on the compression if it does not have a lot of time on it. I've got an 039 I bought used that is showing 160. But they'll run way below 150; I think most people would say they will not run well below 110 or so. My 046 bought used is 16 years old and still blows 168; it was only run maybe 20 days a year though.

I'd want to see a 16" bar on a 250; any longer and I'd have to take into account the potential need to get a shorter bar and chain. They are good little saws but have a fair amount of plastic. See if the plastic case is chipped behind the clutch. If the chain has been thrown often it may be beat up. I think they also have a plastic stub that keeps the clutch case apart from the crankcase and also serves as a chain catcher. See if it is intact or broken.

Check the air filter to see if it is clean or covered in crud.

The other tried and true check is to pull the muffler and inspect the exhaust side of the piston for scars.

On most of them, when cold starting you will not hear the pop from a misfire that tells you it's time for half choke. So set full choke, pull the starter cord twice, then set it to half choke no matter what and start if from there. The carb floods easily on that model, but it's not an issue if you know how to start them.

 

[apn73]

Would you like to know the results of a few comp tests on this engine?

Yes, absolutely, that will be good info to know. Thanks much.

 

[apn73]

Thanks for all the tips fellas, as usual, this forum and the people on it

 

[apn73]

Never had one on a gauge but by feel I'd say a used one should blow 145ish

Congrats on the new business venture by the way, hope it works out well for you. What happened to your new avatar? That wasn't up long.

 

[ptjeep]

As somebody else mentioned, the fuel lines are know to cause idling/running issues once they get old. Give that a quick visual while you're checking it out.

 

[o8f150]

if I remember right this one that I built was right at 145

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[ohio andy]

The one I bought this spring that appears to have many hours on it blew 150 psi on a good amazon tester. It runs well and starts as it should.

 

[FergusonTO35]

If you use a regular automotive gauge with a long hose your readings will probably be 20-50 psi low.

 

[apn73]

If you use a regular automotive gauge with a long hose your readings will probably be 20-50 psi low.

Are you talking about the rubber tip as opposed to the threaded adapters?

 

[Adirondackstihl]

If you use a regular automotive gauge with a long hose your readings will probably be 20-50 psi low.

My Snap-On gauge works just fine :msp_confused:

 

[FergusonTO35]

Maybe my gauge is bad or I'm doing it wrong. I have a Matco gauge with the rubber hose and screw on fittings, it hasn't been used much and I bought it new. Dry, pretty much all of my great running saws blow 100-110, including my low mileage Echo CS-400. I'm doing it the same way I test a 4 cycle. Hook up the gauge, block the throttle open, and pull until the gauge won't go any higher. Usually it takes 5-10 pulls. To check the rings I add a little 2 stroke oil and then repeat to see if there is much of a difference. Am I doing it wrong?

 

[apn73]

By the way, what is a fair price for one of these saws in fair to good condition. The guy is asking $175 for it and that seems a little high, he claims that his Dad (passed away last year) only used premium fuel and synthetic oil, but it looks kind of dirty in the photo. I know that doesn't mean much, but it looks a little rougher than some of the other saws that I have seen for $150-$200.

 

[Adirondackstihl]

Maybe my gauge is bad or I'm doing it wrong. I have a Matco gauge with the rubber hose and screw on fittings, it hasn't been used much and I bought it new. Dry, pretty much all of my great running saws blow 100-110, including my low mileage Echo CS-400. I'm doing it the same way I test a 4 cycle. Hook up the gauge, block the throttle open, and pull until the gauge won't go any higher. Usually it takes 5-10 pulls. To check the rings I add a little 2 stroke oil and then repeat to see if there is much of a difference. Am I doing it wrong?

Your gauge is reading low. A good running saw with low mileage should be in the 145-165 range depending on the saw.
Blocking the throttle wide open is completely a waste of time.
Why add oil to the cylinder to check rings? Sounds like the only thing youre checking by doing that is the gauge?

By a GOOD gauge or check your saws with someone elses.

EDIT: Excess oil the cylinder can give extremely false (high) comp readings. Don't do it.

 

[Adirondackstihl]

By the way, what is a fair price for one of these saws in fair to good condition.

$50

 

[apn73]

$50

Seriously?

 

[FergusonTO35]

Your gauge is reading low. A good running saw with low mileage should be in the 145-165 range depending on the saw.
Blocking the throttle wide open is completely a waste of time.
Why add oil to the cylinder to check rings? Sounds like the only thing youre checking by doing that is the gauge?

By a GOOD gauge or check your saws with someone elses.

EDIT: Excess oil the cylinder can give extremely false (high) comp readings. Don't do it.

Thanks for the advice. I'll check it against another gauge and see if there is a difference. As far as blocking the throttle open and adding oil the second time to check the rings, that is how it is done on a 4 cycle and I didn't know any better. I'm still fairly new to working on 2 cycle other than basic maintenance.

On MS-250 prices, there was a cherry one in a nearby pawnshop for $175.00 last month. They don't seem to command the premium of the proline saws or even the old 0-series, at least around here.