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394 XP Heat Problem

Discussion in 'Chainsaw' started by 2FatGuys, Mar 10, 2008.

  1. 2FatGuys

    2FatGuys AboristSite Guru

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    Yesterday, I was working my 394XP pretty hard. We were firewooding a 52" Willow Oak, cutting off 16" slabs, then ripping them small enough to handle getting to the splitter. I was running tank after tank of gas through it. After about 4 1/2 hours, the brake handle got so hot that the rubber / plastic slumped down and warped. Also, the plug wire, which runs adjacent to the cooling fins on the cylinder, melted through ands shorted out.

    We plan to check the piston, rings and cylinder for damaged since it got that hot. What would cause such a spike in temperature so quickly after running perfectly all morning? We want to avoid this happening again.
     
  2. 2FatGuys

    2FatGuys AboristSite Guru

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    Bumping the post back up, hoping for some educated input.
     
  3. 2dogs

    2dogs Addicted to ArboristSite

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    First off did you ever give the saw some downtime to cool? I would check the fins for build up of sawdust. Ripping causes build up pretty fast.
     
  4. nikocker

    nikocker Addicted to ArboristSite

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    Oh Yeah!

    That's how I cooked my 261 last year. Rippin blocks and didn't notice the fins clogging.
    Al:(
     
  5. slabmaster

    slabmaster AboristSite Guru

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    It might had aquired an air leak during the day and is running to lean. Check your seal on the clutch side.It may have failed due to the extra strenous work.
     
  6. Junkwrencher

    Junkwrencher ArboristSite Operative

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    394 heat problems

    Something I've experienced is loose or broken muffler bolts especially on one side, if both break you'll notice an increase in noise, one breaks and you loose compression if you're lucky...I agree on the cooling fins/sawdust build-up also....
     
  7. stevethekiwi

    stevethekiwi Addicted to ArboristSite

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    loose spark arrestor / muffler directing exhaust where it shouldn't... maybe?

    had that before...

    i can mill all day with the 395 (its the same saw pretty much) and the fins dont attract that much junk - but u still need to keep an eye on them just in case ;)

    when i run a double ended mill with the 395's, the saw that runs backwards fills up the clutch cover with $hit in no time... a mixture of dust and oil.. that gets the heat cranking :chainsaw: :chainsaw:
     
  8. 2FatGuys

    2FatGuys AboristSite Guru

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    Thanks for the input. I'll be cleaning this saw up tonight.
     
  9. Scooterbum

    Scooterbum Addicted to ArboristSite

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    +1 on the fins stopped up.But more likely then not you were running too lean.
     
  10. 2FatGuys

    2FatGuys AboristSite Guru

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    Too Lean?

    This saw has been a major workhorse in our stable. It has been a reliable performer for quite a while. There were no adjustments done to the carb after setting it to "4-stroke" in the cut several weeks ago. We worked it hard Friday with no problems and then after 4 1/2 hours, it burned through the plug wire.

    With the exception of a possible sudden air leak, as mentioned earlier, I can't buy the "too lean" theory. I'm not saying that running lean wasn't the problem. I'm only saying that there is a much deeper reason to WHY it may have run lean. How can we check the seal on the clutch side for air leak? Are there other common sources of leaks?
     
  11. kurtty

    kurtty ArboristSite Operative

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    check the black intake boot by the fly wheel. i had the screw vibrate loose and knock that thing into peices on me on my 365. cooked the piston on that saw after it got whicked hot.
    with out that intake boot your saw will be taking in hot air from by the cylinder and not cool air off the fly wheel.
    but it could just be that you had it going for 4 and a half hours wihtout stoping.
    but check your high jet first. its probably just a slight bit lean and after using it for such a duration it added up to alot of heat.
     
  12. 2FatGuys

    2FatGuys AboristSite Guru

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    Intake boot?

    Kurtty - Huh? On the 394, the intake air is swirled at the flywheel, behind a grey plastic "induction shield" and "injected" through the plastic case to the air filter chamber. From there, the air travels through the filter and through a black plastic elbow into the carburator. What "intake boot" are you talking about? I've never seen one on this saw, nor in the service manual.
     
  13. slabmaster

    slabmaster AboristSite Guru

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    That's because you don't have one!Like i said earlyier you probably have an air leak somewhere else.Maby a seal went.Presureize your case to make sure or you could cook a cylinder,piston,or rings. Mark
     
  14. 2FatGuys

    2FatGuys AboristSite Guru

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    Other than all the "clean the fins" replies, your air leak seems most plausible. I've worked this saw hard plenty of times in the past with no problems. My initial once-over when it quit showed no torn filter or loose carb or muffler bolts. I was wondering how it could have leaned out so suddenly.

    How much should I pressurize it?
     
    Last edited: Mar 11, 2008
  15. SawTroll

    SawTroll Information Collector

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    What sory of ripping is this about really - ripping from the side is not very taxing on saws, as far as I understand - doesn't feel like it is either........
     
    Last edited: Mar 11, 2008
  16. 2FatGuys

    2FatGuys AboristSite Guru

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    We were ripping (WITH THE GRAIN - creating long chips, rather than down the grain - creating fine dust) 16-18" rounds slabbed off of a 52" willow oak. It's EASY cutting, but it does create a LOT of spaghetti strings. I try to keep the saw angle such that it clears the chips from the clutch cover rather than clogging up. I didn't check the fins though. Tonight's tear down is going to tell a lot I hope.
     
    Last edited: Mar 11, 2008
  17. Junkwrencher

    Junkwrencher ArboristSite Operative

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    One more thing I failed to mention, the intake itself, they crack, which causes a lean condition, I've replaced two on two different saws.The 395 which replaced the 394 has a rubber intake, the 394 however is a heat insulater type rigid material, did you chech your muffler bolts???
     
  18. nikocker

    nikocker Addicted to ArboristSite

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    Right On.

    That's exactly it. The ripping itself isn't that taxing although the bar is buried in the length of the block almost constantly. What got me and cooked the saw is that I didn't notice the curlys plugged the fins behind the shroud . . . couldn't easily see them. :cry: :cry: :cry:

    Al
     
  19. kurtty

    kurtty ArboristSite Operative

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    sorry, i was talking about the plastic peice that guides the air from the fly wheel into the compartment that holds the carb and airfilter.
    the peice of plastic that you replace with a blue one when installing a winter kit.
     
  20. romeo

    romeo Addicted to ArboristSite

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    Mod the muffler. It will be a little louder but it will disperse allot more heat. Milling is he!! on a saw and I would use every trick I could to keep it cool.
     

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