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Stihl 025 Problem

Discussion in 'Chainsaw' started by acbell, Mar 10, 2008.

  1. acbell

    acbell ArboristSite Lurker

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    Hi,

    I have a seven-year old 025 that has run well until recently. In the very cold (0-25), the saw doesn't want to idle - it cuts out instead. It also has very little power before it warms up (putting it to wood makes it dies). I took it to the dealer who put in a carb kit, replaced the plug and fuel filter, cleaned the exhaust screen. He also said that the cylinder showed signs of pre-ignition (supposedly due to low-octane gas). Symptoms are still the same.

    Any thoughts on what might be wrong? I am perfectly willing to fix this myself, but I don't know how to tell what is wrong. Can anyone help? Is it worth fixing this saw?

    Thanks in advance,

    -- Andrew Bell
    andrew.bell.ia@gmail.com
     
  2. Lakeside53

    Lakeside53 Stihl Wrenching

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    What is your compression?
     
  3. Fish

    Fish Account Hold

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    We can assume that the fuel line is not full of cracks, since it has been in
    the shop, but it sounds like you might want to look at the impulse line, It
    attaches on a nipple on the lower end of the cylinder and runs up to
    a plastic nipple on the inside of the rear handle, right behind the carb, it is
    likely pulled loose there. After this many years, the rubber might be losing
    its pliability, and need replaced. Also check for av mounts pulled out, as this will pull the line off too.
     
  4. acbell

    acbell ArboristSite Lurker

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    Saw Update

    Thanks for your ideas. Sorry to take so long to follow up - busy.

    I put an auto compression guage on it and it came out at about 67. Is this an OK way to test? What is good compression for this engine?

    Pulled the cover off and found the impulse line. Looks OK. I didn't understand how it was connected until I pulled the cover so I don't know if it was connected before. Anything else to check before I reconnect and reassemble to see if the impulse line might have been disconnected and the problem?

    Thanks,
     
  5. THALL10326

    THALL10326 The Champ

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    67 lbs, its dead. In fact at 67lbs it shouldn't even start. Check your gauge reading again, something tant right...
     
    Last edited: Mar 22, 2008
  6. Lakeside53

    Lakeside53 Stihl Wrenching

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    You have the wrong gauge.... or a really dead saw!

    I'd expect 140-160....
     
  7. treeclimber jul

    treeclimber jul ArboristSite Operative

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    Recheck psi gage, sometimes the shrader valve lets pressure bye.
     
  8. ropensaddle

    ropensaddle Feel Lucky

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    Just in case you don't know several pulls are needed to check compression
    on your saw!
     
  9. Erick

    Erick Addicted to ArboristSite

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    Probably the wrong style gauge, you need one with the schrader valve at the end of the hose where it goes into the spark plug hole.

    Like Tom said it shouldn't even run at 67lbs.

    I ass-u-me your dealer set the fuel mixture???

    Might just be a simple L adjustment?

    Your saw might be running lean and starving for fuel or running rich and flooding. Turn the L screw in an 1/8th of a turn and see what happens if it gets worse turn it back to where it was and then turn it out an 1/8th of a turn.

    If something helps go a 1/4 turn and see what happens, you might have to readjust the LA screw to adjust the idle speed if you have to make to much adjustment to the L screw. Just make sure you know where all the screws are set when you start and can put them back to the original settings if you need to. I don't recommend you turn any of them more than 1/2 a turn, if it's not helping your problem put them back to where you started, it's another problem.
     
  10. stihl025

    stihl025 AboristSite Guru

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    I am assuming that this is not a "modded" saw. No muffler mods or anything like that? I would almost start from scratch with the L and H settings and go from there... Who knows what the dealer did or didn't do when it comes to adjustment. Not sure what your saw requires, but mine was -1 full turn each from the seat. I just replaced a fuel line and had to "start" over, and the settings that I used to have no longer worked because of no more air leaks. The basic settings got the saw runnings good enough to fine tune it. No problems running or idling since.
     
  11. acbell

    acbell ArboristSite Lurker

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    Compression Guage

    OK,

    I'll assume I have the wrong guage since the saw did run when it was warmer out. The one I have just has a hole in the brass fitting that screws into the spark plug hole and a pressure release right next to the guage about a foot away. Can I get some other style guage at an auto-parts store, or is it special for two-stroke engines?

    Thanks!

    -- Andrew Bell
     
  12. Erick

    Erick Addicted to ArboristSite

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    Yep wrong gauge, nothing special about the gauge for a saw it just has to have the valve at the end of the hose. The combustion chamber on a saw is pretty small, and with the valve at the gauge end of the hose, the chamber has to fill the length of hose with air on each stroke causing it to read low. Whereas the valve at the end the hose allows it to hold pressure letting it be pumped up to match the cylinder pressure and get an accurate reading.

    You might be able to get a new hose for your gauge with the valve at the end??
     

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