Compression on Stihl 025

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Kenw

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I have an old stihl 025 that I bought new back in around 2000/2001 and it has been a good firewood saw for me. I have acquired a few more different saws and thought I should pick up a compression tester and see where they were all at. I bought the innova 3614 tester. I have a Stihl 025/16", MS362/20", 044/24", and a Jonsered 2051/18". I just did a carb kit on the 025 and the 044. These are the results I got:

Stihl 025 compression was 90 (first test I did, warmed the saw up and had the air cleaner off)
Stihl MS362 compression was 120 (cold, air cleaner on) (I bought this one used)
Stihl 044 compression was 145
Jonsered 2051 was 152

The reason I did the carb kit on the 025 is because it wouldn't stay running when it was warm...if I set it down it would die and then be flooded and hard to start. I'm thinking I wasn't supposed to warm it up to do the test, but wondered what the rule of thumb is on that. I will have to try it again cold.
Is 90 quite low even warmed up?
The 362 runs good, but is 120 a little low? Paid $375cdn and it has the extra handle and heated grips and carb so i think it is worth keeping.

Thanks for any input!
 
Thanks, seems strange that it runs good now that I did the carb...I haven't ran it cutting a bunch yet though. Not sure if it is worth fixing. I am mechanically inclined but have never gone beyond carb kits etc.
 
The 025 is a pain to tear down (No real learning curve) but very simple motor. Be worth trying seals and rings. Little motoseal or dirko all ya need no base gasket.

Not much money. Just have to figure out if it's 42mm or 42.5mm version.

Be a confidence builder before tackling the 362.
 
The 025 is a pain to tear down (No real learning curve) but very simple motor. Be worth trying seals and rings. Little motoseal or dirko all ya need no base gasket.

Not much money. Just have to figure out if it's 42mm or 42.5mm version.

Be a confidence builder before tackling the 362.


Yes, that is a good point...I will have to do the 362 sooner than later I guess. Just bought the dang thing and have only dropped a dozen trees with it. Love the saw though. Thinking of buying a new ms261c pro saw to replace the 025, but will wait until next year.
 
Are you pulling many times, till the gauge stops climbing?

I don't think it climbed much after the 3rd pull. Pulled 10 times and then released it and pulled another 10. She was flooded real bad after that
 
I bought my 025 a year before you. I was going to sell it a couple of years ago and buy a MS241, but several people here advised me so keep it. It's a great small saw and better than it's supposed to be. I would repair it if I were you.
 
I bought my 025 a year before you. I was going to sell it a couple of years ago and buy a MS241, but several people here advised me so keep it. It's a great small saw and better than it's supposed to be. I would repair it if I were you.

I think I will too...be good experience for me, as I have never done any motor work. Google will be my friend!
 
I could be wrong but thought warm ( not hot or cold ) was the standard procedure. Test with wide open throttle, I pull until it quits climbing. Any way I don't trust readings to be very accurate on any of the last 3 gauges I bought. Had a new gauge that was about 30# low on readings once. Sold on ebay I don't know how many saws before I realized. Cost me for using low inaccurate readings. I think the 2 gauges I have now read a little low also, 1 reads near 10#s higher then the other.
Haven't found any thing yet I like better in that price range - weight - power then the 025. I'd like to try some other models but wouldn't consider replacing my 025's on here say. Recently traded a Jonsered 2141 for an ms251. I want to run this with my work 025 for comparison. For limbs and smaller wood I prefer the 025 over the 026. Bigger stuff I usually prefer upping up to 60 or 70ccish. Steep ditch banks when I need just a little more umph is usually when I use an 026.
 
I could be wrong but thought warm ( not hot or cold ) was the standard procedure. Test with wide open throttle, I pull until it quits climbing. Any way I don't trust readings to be very accurate on any of the last 3 gauges I bought. Had a new gauge that was about 30# low on readings once. Sold on ebay I don't know how many saws before I realized. Cost me for using low inaccurate readings. I think the 2 gauges I have now read a little low also, 1 reads near 10#s higher then the other.
Haven't found any thing yet I like better in that price range - weight - power then the 025. I'd like to try some other models but wouldn't consider replacing my 025's on here say. Recently traded a Jonsered 2141 for an ms251. I want to run this with my work 025 for comparison. For limbs and smaller wood I prefer the 025 over the 026. Bigger stuff I usually prefer upping up to 60 or 70ccish. Steep ditch banks when I need just a little more umph is usually when I use an 026.

Yep, not trusting reading from just one gauge is why I used some compression tester tips from this link and built my 2nd own compression tester for small engines. Automotive type gauges will usually read low and even some of the small cc gauges will intermittently read low. After getting the correct type Schrader valves and locate them right at the spark plug adapter. The low dollar, low pressure, 700-9556 Napa Schrader valves work great and also the type I mention in this article that I modded.

Keep a spare Schrader valve handy because a small piece of carbon will eventually get into the valve and not back check compression.

http://www.arboristsite.com/community/threads/compression-tester-issues.310133/
 
The 025 really is a decent saw if maintained right and proper fuel and oil is used in it. Some say they're hard to rebuild but they just take a little more time because there's a bit more to remove to get the engine out of it. I've rebuilt a bunch of them and the 290 version also. Just be sure to put new crank seals in it while you have it apart. I use Motoseal for the pan sealer, less messy than Dirko..
 
Schrader valves with a very weak spring are available on Ebay and elsewhere. There are necessary for an accurate reading. If you think your gauge is reading low try replacing the valve to be sure you have the right one. Also the Schrader valve MUST be at the point of attachment to the cylinder to be accurate. I make mine from old spark plugs. If the valve is further up toward the gauge, the extra tubing adds volume to the cylinder and the reading will be lower. Dosen't really matter if you are measuring compression on a 427 V-8, but it makes a real difference with small cylinder chain saw.
 
Schrader valves with a very weak spring are available on Ebay and elsewhere. There are necessary for an accurate reading. If you think your gauge is reading low try replacing the valve to be sure you have the right one. Also the Schrader valve MUST be at the point of attachment to the cylinder to be accurate. I make mine from old spark plugs. If the valve is further up toward the gauge, the extra tubing adds volume to the cylinder and the reading will be lower. Dosen't really matter if you are measuring compression on a 427 V-8, but it makes a real difference with small cylinder chain saw.

I think the gauge is fairly accurate...the schrader valve is quite soft. I just bought my wife a new Stihl MS170 and it hasn't been run yet other than initial startup and tuning. The gauge read just over 150. My saw is an hour away at my cabin, but next time I go up I will check it again cold. Thanks for the info!
 
Just wanted to update, after getting my saw on the compression tester again - I did it from cold and it came in at 120 psi. Runs great and still performs good still. Going in to get a 261cm tomorrow. Too bad I can't use it for a week though!
 
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