Thinking my chainsaw blew up - Page 2
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  1. #26
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by Hobbytime View Post
    pistons in the huskys at big box are cast...from equipment dealer they are forged, my friend that has been doing small engine repair for ever can tell a big box store stuff because whats metal parts from the dealer is usually plastic pieces in the big box.. if you go look at the same model numbers in the big box stores they usually have a different letter or number after the model that equipment dealers dont have, maybe sthil is different , they say they only sell at dealers, but ace hardware sells them..toro, Milwaukee, many of the tools do this, go buy a schlage lock at big box and then goto a locksmith..too differently made units...this goes for most of what they sell..

    Ummm, nope, not true for gasoline power equipment. I've been a licensed small engine mechanic for over three decades, worked for myself as a full line dealer for Stihl for twenty years and am currently self employed as the local authorised Husqvarna and Echo warranty agency and I know that there are NOT different parts for the same model depending on where they are sold. It's a line that some people like to promote as the difference between big box and independent dealers, but it's just a myth.....not true.

  2. #27
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by John Bartley View Post
    Ummm, nope, not true for gasoline power equipment. I've been a licensed small engine mechanic for over three decades, worked for myself as a full line dealer for Stihl for twenty years and am currently self employed as the local authorised Husqvarna and Echo warranty agency and I know that there are NOT different parts for the same model depending on where they are sold. It's a line that some people like to promote as the difference between big box and independent dealers, but it's just a myth.....not true.
    ok, ill take your word on it, ive had several people that repair equipment as their business tell me that the big box stuff is different.....

  3. #28
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    Re: Thinking my chainsaw blew up

    To the OP, next time remember, troubleshoot first, then repair. Since you don't know what went wrong there is a good possibility that you will replace a bunch of stuff, reassemble and still have a problem.
    Personally I suspect that your stuck decompression lever was causing low compression.

  4. #29
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    Re: Thinking my chainsaw blew up

    I agree if the decompression valve was stuck or loose it will lean the engine. The MTronic will automatically richen the mixture to it's maximum capacity then it will run lean


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  5. #30
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    Re: Thinking my chainsaw blew up

    New type 2 cycles must blow up in a far prettier fashion than I am used to.
    I used to see holes in pistons,scored cylinder walls,chewed up rings and ground up roller bearings.

  6. #31
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    Re: Thinking my chainsaw blew up

    compression only comes frome one thing,, how close the piston comes to the head and how tight the rings keep the compression contained, you might have other problems but i would suggest u fix the one problem u know u have,, compression numbers, put a new set of rings in there after making sure the cylinder bore is very smooth,, u might have blown a crankcase seal also but, again i would fix compression, reassemble the powerhead, try iot, then fix seal if it calls for it,, carb if needed, whatever, good luck buck, while u have it together i would suggest doing the cranckcase vacuum and pressure test to exclude seal problems,, buck
    Last edited by buck; 07-16-2017 at 02:35 PM. Reason: add additional info

  7. #32
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by motolife313 View Post
    Tried cutting some big oak and about 4 minutes in my saw dies and didn't want to start after and the compression release wouldn't even kick off. Didn't really care becuse I think this saw is a piece of crap anyway since you can't adjust anything on it. Not even the idle. Gained some compression back when I got it home and kinda fired a couple times. Took it apart and piston looks really good. Compression gauge only read 95 psi though. That sound low? It blew because it lean itself out. i had the air filter covered with tape and it was getting me by but I think the tap loosend up maybe just the jug is bad becuse piston looks good
    That piston looks fine. If your compression 95, it's low but not low enough to keep it from running. Was it low with your decompressor stuck open or did you close it before you did the compression test? That plug is way too white, but if the cylinder is as clean as the plug then your saw didn't "blow" .... something else happened. If it was me, I'd go get a new cylinder base gasket, put it back together as-is then do the crankcase pressure/vac test. I'd also do the other common sense checks like fuel tank venting, fuel line holding pressure etc. Then, once I knew what the story is I'd do the necessary repairs, but what I sure wouldn't do is guess at it. There's no point in trying to fix anything until you know what to fix. Some years ago Stihl had an issue with fuel tank vents not working. I think it was on the MS361's?? but I don't remember for sure. Anyway, the problem was that the tank vents would not allow air in and that caused a vacuum lock and the saws starved for fuel.....sound like yours?

    So, once again .... new base gasket ... reassemble as-was .... do the tests .... then fix.

    EDIT :: why was your air filter covered with tape? If you want to screw up your Auto-tune performance, that's a good way to do it. As far as not being able to adjust anything ... you don't have to ... that's the whole point of Auto-tune. If your fuel is clean and fresh, your air filter and spark plug are clean and in good shape, you just run it and let the Auto-tune keep it optimized.
    Last edited by John Bartley; 07-16-2017 at 03:35 PM.

  8. #33
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by John T View Post
    24"
    and yeah, it's heavy.

    it's a big boy saw...

    No, that's a midsize saw and fairly light weight. I'll guess it weighs less than 16 pounds fuel of fuel and oil, wearing that 25" B/C. My Husqvarna 394xp weighs 17 pounds before fuel/oil/bar and chain. On a shelf in my shop there is an old Homelite 750...120cc powerhead that weighs around 22-24 pounds dry, no bar/chain.

    Real "big boy" saws require two men to run. The examples I have buried somewhere out in my shop weigh around 100lbs ready to cut wood, and use 7/8" pitch chain.
    Logging was hard work before mechanization.
    Not me, or anyone I know.


    As far as your compression problem goes, I'll guess that the rings have lost tension or that you have a bad decompression valve. Sometimes those valves fail. Some guys just take the valve out and put a plug in it's place.

  9. #34
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by walker View Post
    To the OP, next time remember, troubleshoot first, then repair. Since you don't know what went wrong there is a good possibility that you will replace a bunch of stuff, reassemble and still have a problem.
    Personally I suspect that your stuck decompression lever was causing low compression.
    Could be broken de compression valve, not sure yet. It was really easy to pull with valve pushed in and harder when pulled out as in it working. I'm just Gina hone the cylinder put new rings on and hopefully it will be good. If it don't start I'll stick a bolt where the valve is and try it without it. I've been wanting to do this for a while
    Last edited by motolife313; 07-16-2017 at 10:54 PM.

  10. #35
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    Re: Thinking my chainsaw blew up

    Decompression valves have been known to fail and are cheap. I've replaced a few and chainsaws are well outside my normal scope of work.
    My name's not Jim....

  11. #36
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by machinisttx View Post
    No, that's a midsize saw and fairly light weight. I'll guess it weighs less than 16 pounds fuel of fuel and oil, wearing that 25" B/C. My Husqvarna 394xp weighs 17 pounds before fuel/oil/bar and chain. On a shelf in my shop there is an old Homelite 750...120cc powerhead that weighs around 22-24 pounds dry, no bar/chain.

    Real "big boy" saws require two men to run. The examples I have buried somewhere out in my shop weigh around 100lbs ready to cut wood, and use 7/8" pitch chain.
    Logging was hard work before mechanization.
    Not me, or anyone I know.


    As far as your compression problem goes, I'll guess that the rings have lost tension or that you have a bad decompression valve. Sometimes those valves fail. Some guys just take the valve out and put a plug in it's place.
    The 385 weights 21 pounds I looked it up. Husky claimes 15 but that ain't true. My 361 weights 17 pounds

  12. #37
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by Bluewelders View Post
    New type 2 cycles must blow up in a far prettier fashion than I am used to.
    I used to see holes in pistons,scored cylinder walls,chewed up rings and ground up roller bearings.
    Yep. "Blown up" usually means you now have more parts than the engine was assembled with.
    My name's not Jim....

  13. #38
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by motolife313 View Post
    I'm just Gina hone the cylinder put new rings on and hopefully it will be good.
    There's nothing to hone inside that cylinder. The second you touch it with a honing stone it's toast. Don't waste your time and money.

  14. #39
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by John Bartley View Post
    There's nothing to hone inside that cylinder. The second you touch it with a honing stone it's toast. Don't waste your time and money.
    Nikasil ?
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  15. #40
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by machinisttx View Post
    No, that's a midsize saw and fairly light weight. ..
    20 years ago it was light weight.

    it's manageable but I ain't climbing any trees with it....

    I like it to buck up firewood... I get it delivered in tree lengths so with a long bar I don't bend over as much ...

    I'm kinda picky about saw care, each tank of gas I let it cool down.... drink a beer.... then blow out the entire saw with compressed air and touch up the chain with a file.

    been a good method..
    knock on wood.
    Miller 211/Spoolmate 100
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    True Wisdom only comes from Pain.

  16. #41
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by John T View Post
    Nikasil ?
    I've been long enough away from Stihl (several years now) that I've not taken the tech training on that saw, so I don't know if the cylinder wall is hardened or plated, but either way, if you can feel a score it's thru' the hard surface. If you can feel a ridge, then it's from aluminum transfer from the piston and can sometimes be removed. The OP's piston looks flawless so I doubt there's any transfer and if the cylinder looks as good as the piston, then honing it will ruin a perfectly good cylinder. Changing rings on a "guess" without even sliding an old ring up into the bore to measure the ring end gap is pointless. Doing any repairs without doing the pressure/vac test is pointless. The cheapest, fastest way to get a good repair is to spend the money on a new cylinder base gasket (to eliminate the chance of leaks there), then reassemble and do the tests that should have been done before taking it apart the first time.

    I'd still like to know why the air filter was taped over ..... the auto tune will sense the obstruction at the intake, then reduce the fuel flow to try and maintain an optimum mixture. If the inlet is badly enough obstructed the fuel flow will diminish to the point where the saw stops running before a lean seizure or over rich condition occurs. It sounds to me like the saw is doing everything it can to save itself in spite of it's owners worst intentions.

  17. #42
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by John Bartley View Post
    I'd still like to know why the air filter was taped over ..... the auto tune will sense the obstruction at the intake, then reduce the fuel flow to try and maintain an optimum mixture. If the inlet is badly enough obstructed the fuel flow will diminish to the point where the saw stops running before a lean seizure or over rich condition occurs. It sounds to me like the saw is doing everything it can to save itself in spite of it's owners worst intentions.
    Now thats funny.................

  18. #43
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by Hobbytime View Post
    Now thats funny.................

    Yes, now that I read it again it is a bit funny, but ..... it was meant with no insult intended. Plenty of folks, familiar with older saws, who are used to a saw "sounding" a certain way and who would adjust them to run best "for them" have a hard time letting a piece of machinery do their tuning for them, then get frustrated when they don't see the results that they are accustomed to. It's an education process.

  19. #44
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    Re: Thinking my chainsaw blew up

    The tape is there because it's not a very good auto tuning saw. Does the plug look like it had a good auto tune. The tap was getting me by for a while. Restricting the air and it richend it up a lot but the tap kinda loosened up after not using it for about a month

  20. #45
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    Re: Thinking my chainsaw blew up

    Im not a big fan of computer controlled equipment or tools...they have a built in life span and more parts to spend $$$ on, if you will be able to find the computer parts in the future..is there anyway to get rid of the auto tune on that saw?

  21. #46
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    Re: Thinking my chainsaw blew up

    I'm hoping I can but not sure

  22. #47
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    Re: Thinking my chainsaw blew up

    Quote Originally Posted by motolife313 View Post
    The 385 weights 21 pounds I looked it up. Husky claimes 15 but that ain't true. My 361 weights 17 pounds
    Where are you getting those numbers from? I don't know that I have ever put any of my saws on a scale. The 394 gets heavy pretty quick when I put the 32" bar on it....not too bad with the 24" it usually wears.

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