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dolmar 112 woes

Discussion in 'Chainsaw' started by 1953greg, Mar 8, 2008.

  1. 1953greg

    1953greg AboristSite Guru

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    saw will barely run enough to get the cylinder too hot to touch. i have ruled out everything but the tollitson carb. floods continously.

    now what? rebuild carb? or is something adjustable?
     
    Last edited: Mar 8, 2008
  2. Javelin

    Javelin Addicted to ArboristSite

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    Have you rebuilt the carb? The old tillotson carbs used on those had a replaceable needle and seat block! If you replace it and the diaphrams you should be good to go!
     
  3. spacemule

    spacemule The Peanut Gallery

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    I'm not well versed in saw troubleshooting, but assuming you've got good spark, if it's constantly flooding, that would be a carb problem.
     
  4. 1953greg

    1953greg AboristSite Guru

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    i have had bad diaphrams before (this one is ok) and the saw has no gas to run on. so how does the needle & seat block go bad? not questioning your info, just curious?
     
    Last edited: Mar 8, 2008
  5. doubletodd

    doubletodd ArboristSite Operative

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    my tillotson had something stuck in the seat block that the could'nt get out, so they told me
     
  6. pioneerguy600

    pioneerguy600 Tree Freak

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    Does your 112 have the plastic seat block? These are nothing but trouble on the tillotson HK carbs. Replace it with a metal seat block and make sure that the needle valve itself is made of metal with a neoprene tip and that should take care of the flooding problem. It did on two of my 112`s
    Pioneerguy600
     
  7. 1953greg

    1953greg AboristSite Guru

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    not sure if its a hk but there is a 442 stamped on it.
    is the hk standard on 112's?

    i think the reason it was flooding was because both jets were out bout 1.5 turns. the saw belongs to my pastor.

    took the carb apart. clean inside. needle & seat will prevent fuel flow. even ether. depress the needle and fuel drips, release and it stops. i did not remove needle. diaphram looked ok. elastic and intact. put everything back together and finally got the saw running, but barely. i can set the lo jet to 3/4 and hi jet to bout 1 and get it started then hi to bout 7/8 will get rpms up to 11k, wot w/o b&c, but it wont idle at those settings. has to be 1/8-1/4 richer to start.
    compression is 150.

    summary: saw will barely run and the range of carb settings where it wil run is very narrow. only 1/8 turn. and when it is running it wants to stall and fall on its face. i know it sounds like the lo is too lean but ive tried it everywhere

    obtw this carb dosent have an impulse line. it uses a hole from bottom of intake through boot into carb.

    the only carb issues i have had before is bad diaphram, which results no gas being pumped.

    the symptom is like a saw that has a crack in the fuel supply line sucking air and runs erratic but i eliminated fuel supply issue by using an elevated vented syringe strapped to handle.

    question:
    1. if needle is not leaking and diaphram is intact, can the carb still need a kit?
    2. could there be an air leak like where the parts of the carb join?

    this one is bout to drive me crazy. bet ive yanked on it a thousand times!! its gratuity and in my spare time but i would eventually like to get it done!!!
     
  8. 1953greg

    1953greg AboristSite Guru

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    bump
     
  9. pioneerguy600

    pioneerguy600 Tree Freak

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    I posted a reply earlier on this carb problen but it has not showed up here so I will give it another try,if it shows up eventually it will still contain some helpful hints.
    OK; Yes the HK, was standard on the 112 but some Bing carbs were also used,they are a bit different but work basically the same.
    If everything in carb is clean and set right the saw should run at around 1 turn out on both screws, then fine tune with small adjustments, NEITHER SCREW SHOULD BE SET ANY FURTHER IN THAN 3/4 TURN OUT FROM SEAT, OR ANY FURTHER OUT THAN 1 & 1/4 OUT. If the saw will not run inside these settings something else is wrong.
    It is not likely that there is a leak between the carb parts as the gaskets usually do a good job sealing the carb up tightly. Only if the carb has been damaged by prying apart the covers or the metering module with inappropriate tools or practice and they have become galled or bent.
    Did you remove the setting screws and blow out the passages when you had the carb apart.
    Did you remove the metering lever and inlet needle and clean the well where it sits in and visually check the needle tip for wear or gummy feeling, must be very clean here. The metering lever must be set exactly flush with the carb body on either side of where it pivots on the pin.
    The inlet spring must be in the hole under the metering lever and be properly seated around the dimple under side of the metering lever. Also these springs lose tension with age and sometimes have to be replaced with new ones to work correctly, if it sets bent over side ways when out on the bench it is probably weak.
    There is also a removeable main nozzle in some of this series of carbs that can trap dirt particles or become sticky with age,these are a real problem if not completly clean and not sticky. I just cleaned one of these up the past weekend and it had been giving its owner headaches for over a year,been to two other shops and had rebuild kits installed but would not idle any where it was set at,it was the main nozzle leaking fuel through it and flooding out at idle. Hope this answers some questions. Pioneerguy600
     
  10. 1953greg

    1953greg AboristSite Guru

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    thanks jerry, the dots are connecting

    i disassembled and cleaned everything cept the needle. i figured since it would meter the flow of fuel or ether then it was ok.

    carb kit is in order

    thanks again
    good day greg
     
    Last edited: Mar 18, 2008
  11. 1953greg

    1953greg AboristSite Guru

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    update

    carb is clean throughout, needle jet is like new and does not leak. diaphram is suple and intact.

    i can get the saw to run but is very difficult to start and wil not idle.

    after many tries starting and barely running and blimping the throttle while occasionally choking i can get it to accelerate and smooth out and run wot @11k w/o bar n chain. but it will run smoothly only above bout 4k. and hesitantly accelerates like the L jet is too lean, but richening only floods it. runs best w/ L 3/4 out and H 7/8 out. but still wil not run smoothly below 4k.

    while blowing air into the carb to clear out flooding, at least once i noticed gas/air bubbles coming out around the throttle/butterfly shaft.

    could this b the culprit?

    any ideas? i have run out
     
    Last edited: Mar 20, 2008
  12. 1953greg

    1953greg AboristSite Guru

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    update

    bump
     
  13. pioneerguy600

    pioneerguy600 Tree Freak

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    Not likely as there is no fuel held in that portion of the carb. I find the setting of the fuel metering lever and the cleanliness of the needle valve tip and the well it sits in to be the most sensitive areas on this carb and has caused me more trouble on rebuilds than any other carb.
    Pioneerguy600
     
  14. Russtic

    Russtic ArboristSite Lurker

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    Hi Greg, I have just bought an old Dolmar 112 and am having very simlar problems, will run with both needles about 1/8 of a turn out but then never for very long. Trying to get a carb repair kit, where did you get yours? Did you ever find a solution to the problem? Russ.
     

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