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Trouble continues with Jonsered 535

Discussion in 'Chainsaw' started by heathcom, Jul 7, 2007.

  1. heathcom

    heathcom ArboristSite Lurker

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    I got a new carb kit for the walbro carb but still doesnt seem to be getting gas into the piston chamber.
    Look at pictures here: http://jonseredchainsaw.tripod.com/
    The top picture is the whole setup.
    The second pic is where I removed the top of the carb to show the gaskets. If I blow into the tube where you see my finger, gas pours out of the carb. If I put the brown thin gasket on along with the thicker black one and I blow into that tube, no gas comes out at all as I cant blow into it like its blocked. If I remove the brown gasket and just use the black one as seen in pic 3 and I blow into the tube, gas comes out of the vent hole.
    The compression seems fine and I get spark, just dont know why the gas doesnt flow into the chamber.
    I got the carb kit as suggested from this post: http://www.arboristsite.com/showthre...t=jonsered 535
    Any help would be great.
     
  2. rreidnauer

    rreidnauer ArboristSite Operative

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    Sometimes even a carb kit can't save a carb. Might have to get a new one.
     
  3. wood rat

    wood rat ArboristSite Operative

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    Seems you may have got a "made on monday saw"
     
  4. JeffinIA

    JeffinIA ArboristSite Lurker

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    re

    I`m also working on a saw doing the same thing, but when i hold the float needle down it will let gas in,otherwise It acts as if it were clogged. Do you have the type of carb that has the tube that pulses from the motor to the carb? and is it hooked up ?The carb I`m working with is a walbro HBA-49. It has 2 fuel lines running to it 1 is main fuel line 1 gets vacume from the motor to run the diaphram
     
    Last edited: Jul 7, 2007
  5. PES+

    PES+ Addicted to ArboristSite

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    What you have done does not tell you anything of any meaning and any diaphram type carb will do as you have noted with the fuel pump gaskets removed.

    Take the carb back off and remove the metering diaphram (the one under the steel cover opposite the one in the pic)
    There should be fuel in the metering chamber when you remove the cover.

    Next make sure fuel can get from the screen (in the round hole pic #2) through the needle when you press the lever in.

    I use carb cleaner and spray it into the screen and push the needle open with a finger on the lever.

    Check the impulse hose (the one that attaches to the top of the carb and runs to a nipple on the cylinder base) for any cracks or holes or loose fit.

    Make sure you clear all internal passages inside the carb with carb cleaner and compressed air if you have it available.

    Don't forget to remove the two mixture needles and spray carb cleaner in the holes and verify that it makes it into the throat of the carb (inside)

    The initial setting on these cabs is around 1.5 on both low and high and will likely run best 1.25 low and around 1 high in the summer and a little richer when really cold.

    You either have a break in the impulse hose or the metering passage that runs from the top to the bottom inside the body of the carb is blocked
     
  6. heathcom

    heathcom ArboristSite Lurker

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    Thanks for the reply. I removed the carb again, made sure gas could flow through the needle when pushed down. I took a can of air and cleared out every hole I could see including the two mixture needle holes. I sprayed it down with carb cleaner and put it back on adjusting the two mixture needles a turn and a quarter. I replaced all the fuel lines with clear gas line and even removed the filter incase that was plugged. The filter in the tank looked fine. I watched the fuel line as I cranked away but still, no gas moves up from the tank and into the carb. Now Im thinking that theres no "suction" from the chamber but I at this point I have no idea.... So many trees so little time.....
     
  7. andrethegiant70

    andrethegiant70 Addicted to ArboristSite

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    Maybe a bad leak in the case or base gasket? ....he wouldn't get impulse no matter WHAT he does to the carb.
     
  8. PES+

    PES+ Addicted to ArboristSite

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    It is possible but rare on that type case

    Check the cylinder hold down bolts and make sure none have broken off or have backed way out.

    The bolts in this style saw go through the top of the crankcase and thread into the base
    A horizontally split case
     
  9. HiOctane

    HiOctane Addicted to ArboristSite

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    Are you sure you got the rigght pump diapragm?Doesnt look like the original,the small "flap" doesnt seem to have the same location.Maybe its the pic.Also check your impulse line for cut and if she is connected at the right place on carb.
     
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  10. heathcom

    heathcom ArboristSite Lurker

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    I believe I have found the reason why theres no suction. Looks like a piece of the piston has broken, see the bottom pic here: http://jonseredchainsaw.tripod.com/

    Any ideas on how much and where I can get a replacement?
     
  11. andrethegiant70

    andrethegiant70 Addicted to ArboristSite

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    Ouch! By the way, even if the piston DIDN'T have an enormous chunk out of it, it would be toasted. Good job getting it together to take it apart, though. It looks like enough wear took place that the piston skirt got too thin. Before you just go and buy a piston, I recommend you make good and sure you can clean up the jug. There are a zillion threads on the site. Some folks use hones, others use combinations of emery paper and muriatic acid. Also, since there has been a hunk of aluminum bouncing around in the bottom end, you should look in there pretty carefully to make sure the case or crankshaft isn't cracked.
     

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